Quelle  Codegen.py

# 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/.

# Common codegen classes.

import functools
import math
from operator import attrgetter
import os
import re
import string
import textwrap

from Configuration import (
    Descriptor,
    MemberIsLegacyUnforgeable,
    NoSuchDescriptorError,
    getAllTypes,
    getTypesFromCallback,
    getTypesFromDescriptor,
    getTypesFromDictionary,
)
from perfecthash import PerfectHash
from WebIDL import (
    BuiltinTypes,
    IDLAttribute,
    IDLBuiltinType,
    IDLDefaultDictionaryValue,
    IDLDictionary,
    IDLEmptySequenceValue,
    IDLInterfaceMember,
    IDLNullValue,
    IDLSequenceType,
    IDLType,
    IDLUndefinedValue,
)

AUTOGENERATED_WARNING_COMMENT = (
    "/* THIS FILE IS AUTOGENERATED BY Codegen.py - DO NOT EDIT */\n\n"
)
AUTOGENERATED_WITH_SOURCE_WARNING_COMMENT = (
    "/* THIS FILE IS AUTOGENERATED FROM %s BY Codegen.py - DO NOT EDIT */\n\n"
)
ADDPROPERTY_HOOK_NAME = "_addProperty"
GETWRAPPERCACHE_HOOK_NAME = "_getWrapperCache"
FINALIZE_HOOK_NAME = "_finalize"
OBJECT_MOVED_HOOK_NAME = "_objectMoved"
CONSTRUCT_HOOK_NAME = "_constructor"
LEGACYCALLER_HOOK_NAME = "_legacycaller"
RESOLVE_HOOK_NAME = "_resolve"
MAY_RESOLVE_HOOK_NAME = "_mayResolve"
NEW_ENUMERATE_HOOK_NAME = "_newEnumerate"
INSTANCE_RESERVED_SLOTS = 1

# This size is arbitrary. It is a power of 2 to make using it as a modulo
# operand cheap, and is usually around 1/3-1/5th of the set size (sometimes
# smaller for very large sets).
GLOBAL_NAMES_PHF_SIZE = 256


def reservedSlot(slotIndex, forXray):
    base = "DOM_EXPANDO_RESERVED_SLOTS" if forXray else "DOM_INSTANCE_RESERVED_SLOTS"
    return "(%s + %d)" % (base, slotIndex)


def getSlotIndex(member, descriptor):
    slotIndex = member.slotIndices[descriptor.interface.identifier.name]
    return slotIndex[0] if isinstance(slotIndex, tuple) else slotIndex


def memberReservedSlot(member, descriptor):
    return reservedSlot(getSlotIndex(member, descriptor), False)


def memberXrayExpandoReservedSlot(member, descriptor):
    return reservedSlot(getSlotIndex(member, descriptor), True)


def mayUseXrayExpandoSlots(descriptor, attr):
    assert not attr.getExtendedAttribute("NewObject")
    # For attributes whose type is a Gecko interface we always use
    # slots on the reflector for caching.  Also, for interfaces that
    # don't want Xrays we obviously never use the Xray expando slot.
    return descriptor.wantsXrays and not attr.type.isGeckoInterface()


def reflectedHTMLAttributesArrayIndex(descriptor, attr):
    slots = attr.slotIndices[descriptor.interface.identifier.name]
    return slots[1]


def getReflectedHTMLAttributesIface(descriptor):
    iface = descriptor.interface
    while iface:
        if iface.reflectedHTMLAttributesReturningFrozenArray:
            return iface
        iface = iface.parent
    return None


def toStringBool(arg):
    """
    Converts IDL/Python Boolean (True/False) to C++ Boolean (true/false)
    """
    return str(not not arg).lower()


def toBindingNamespace(arg):
    return arg + "_Binding"


def isTypeCopyConstructible(type):
    # Nullable and sequence stuff doesn't affect copy-constructibility
    type = type.unroll()
    return (
        type.isUndefined()
        or type.isPrimitive()
        or type.isString()
        or type.isEnum()
        or (type.isUnion() and CGUnionStruct.isUnionCopyConstructible(type))
        or (
            type.isDictionary()
            and CGDictionary.isDictionaryCopyConstructible(type.inner)
        )
        or
        # Interface types are only copy-constructible if they're Gecko
        # interfaces.  SpiderMonkey interfaces are not copy-constructible
        # because of rooting issues.
        (type.isInterface() and type.isGeckoInterface())
    )


class CycleCollectionUnsupported(TypeError):
    def __init__(self, message):
        TypeError.__init__(self, message)


def idlTypeNeedsCycleCollection(type):
    type = type.unroll()  # Takes care of sequences and nullables
    if (
        (type.isPrimitive() and type.tag() in builtinNames)
        or type.isUndefined()
        or type.isEnum()
        or type.isString()
        or type.isAny()
        or type.isObject()
        or type.isSpiderMonkeyInterface()
    ):
        return False
    elif type.isCallback() or type.isPromise() or type.isGeckoInterface():
        return True
    elif type.isUnion():
        return any(idlTypeNeedsCycleCollection(t) for t in type.flatMemberTypes)
    elif type.isRecord():
        if idlTypeNeedsCycleCollection(type.inner):
            raise CycleCollectionUnsupported(
                "Cycle collection for type %s is not supported" % type
            )
        return False
    elif type.isDictionary():
        return CGDictionary.dictionaryNeedsCycleCollection(type.inner)
    else:
        raise CycleCollectionUnsupported(
            "Don't know whether to cycle-collect type %s" % type
        )


def idlTypeNeedsCallContext(type, descriptor=None, allowTreatNonCallableAsNull=False):
    """
    Returns whether the given type needs error reporting via a
    BindingCallContext for JS-to-C++ conversions.  This will happen when the
    conversion can throw an exception due to logic in the IDL spec or
    Gecko-specific security checks.  In particular, a type needs a
    BindingCallContext if and only if the JS-to-C++ conversion for that type can
    end up calling ThrowErrorMessage.

    For some types this depends on the descriptor (e.g. because we do certain
    checks only for some kinds of interfaces).

    The allowTreatNonCallableAsNull optimization is there so we can avoid
    generating an unnecessary BindingCallContext for all the event handler
    attribute setters.

    """
    while True:
        if type.isSequence():
            # Sequences can always throw "not an object"
            return True
        if type.nullable():
            # treatNonObjectAsNull() and treatNonCallableAsNull() are
            # only sane things to test on nullable types, so do that now.
            if (
                allowTreatNonCallableAsNull
                and type.isCallback()
                and (type.treatNonObjectAsNull() or type.treatNonCallableAsNull())
            ):
                # This can't throw. so never needs a method description.
                return False
            type = type.inner
        else:
            break

    if type.isUndefined():
        # Clearly doesn't need a method description; we can only get here from
        # CGHeaders trying to decide whether to include the method description
        # header.
        return False
    # The float check needs to come before the isPrimitive() check,
    # because floats are primitives too.
    if type.isFloat():
        # Floats can throw if restricted.
        return not type.isUnrestricted()
    if type.isPrimitive() and type.tag() in builtinNames:
        # Numbers can throw if enforcing range.
        return type.hasEnforceRange()
    if type.isEnum():
        # Can throw on invalid value.
        return True
    if type.isString():
        # Can throw if it's a ByteString
        return type.isByteString()
    if type.isAny():
        # JS-implemented interfaces do extra security checks so need a
        # method description here.  If we have no descriptor, this
        # might be JS-implemented thing, so it will do the security
        # check and we need the method description.
        return not descriptor or descriptor.interface.isJSImplemented()
    if type.isPromise():
        # JS-to-Promise conversion won't cause us to throw any
        # specific exceptions, so does not need a method description.
        return False
    if (
        type.isObject()
        or type.isInterface()
        or type.isCallback()
        or type.isDictionary()
        or type.isRecord()
        or type.isObservableArray()
    ):
        # These can all throw if a primitive is passed in, at the very least.
        # There are some rare cases when we know we have an object, but those
        # are not worth the complexity of optimizing for.
        #
        # Note that we checked the [LegacyTreatNonObjectAsNull] case already when
        # unwrapping nullables.
        return True
    if type.isUnion():
        # Can throw if a type not in the union is passed in.
        return True
    raise TypeError("Don't know whether type '%s' needs a method description" % type)


# TryPreserveWrapper uses the addProperty hook to preserve the wrapper of
# non-nsISupports cycle collected objects, so if wantsAddProperty is changed
# to not cover that case then TryPreserveWrapper will need to be changed.
def wantsAddProperty(desc):
    return desc.concrete and desc.wrapperCache and not desc.isGlobal()


def wantsGetWrapperCache(desc):
    return (
        desc.concrete and desc.wrapperCache and not desc.isGlobal() and not desc.proxy
    )


def indent(s, indentLevel=2):
    """
    Indent C++ code.

    Weird secret feature: this doesn't indent lines that start with # (such as
    #include lines or #ifdef/#endif).
    """

    # We'll want to insert the indent at the beginnings of lines, but we
    # don't want to indent empty lines.
    padding = indentLevel * " "
    return "\n".join(
        [
            (padding + line) if line and line[0] != "#" else line
            for line in s.split("\n")
        ]
    )


# dedent() and fill() are often called on the same string multiple
# times.  We want to memoize their return values so we don't keep
# recomputing them all the time.
def memoize(fn):
    """
    Decorator to memoize a function of one argument.  The cache just
    grows without bound.
    """
    cache = {}

    @functools.wraps(fn)
    def wrapper(arg):
        retval = cache.get(arg)
        if retval is None:
            retval = cache[arg] = fn(arg)
        return retval

    return wrapper


@memoize
def dedent(s):
    """
    Remove all leading whitespace from s, and remove a blank line
    at the beginning.
    """
    if s.startswith("\n"):
        s = s[1:]
    return textwrap.dedent(s)


# This works by transforming the fill()-template to an equivalent
# string.Template.
fill_multiline_substitution_re = re.compile(r"( *)\$\*{(\w+)}(\n)?")


find_substitutions = re.compile(r"\${")


@memoize
def compile_fill_template(template):
    """
    Helper function for fill().  Given the template string passed to fill(),
    do the reusable part of template processing and return a pair (t,
    argModList) that can be used every time fill() is called with that
    template argument.

    argsModList is list of tuples that represent modifications to be
    made to args.  Each modification has, in order: i) the arg name,
    ii) the modified name, iii) the indent depth.
    """
    t = dedent(template)
    assert t.endswith("\n") or "\n" not in t
    argModList = []

    def replace(match):
        """
        Replaces a line like '  $*{xyz}\n' with '${xyz_n}',
        where n is the indent depth, and add a corresponding entry to
        argModList.

        Note that this needs to close over argModList, so it has to be
        defined inside compile_fill_template().
        """
        indentation, name, nl = match.groups()
        depth = len(indentation)

        # Check that $*{xyz} appears by itself on a line.
        prev = match.string[: match.start()]
        if (prev and not prev.endswith("\n")) or nl is None:
            raise ValueError(
                "Invalid fill() template: $*{%s} must appear by itself on a line" % name
            )

        # Now replace this whole line of template with the indented equivalent.
        modified_name = name + "_" + str(depth)
        argModList.append((name, modified_name, depth))
        return "${" + modified_name + "}"

    t = re.sub(fill_multiline_substitution_re, replace, t)
    if not re.search(find_substitutions, t):
        raise TypeError("Using fill() when dedent() would do.")
    return (string.Template(t), argModList)


def fill(template, **args):
    """
    Convenience function for filling in a multiline template.

    `fill(template, name1=v1, name2=v2)` is a lot like
    `string.Template(template).substitute({"name1": v1, "name2": v2})`.

    However, it's shorter, and has a few nice features:

      * If `template` is indented, fill() automatically dedents it!
        This makes code using fill() with Python's multiline strings
        much nicer to look at.

      * If `template` starts with a blank line, fill() strips it off.
        (Again, convenient with multiline strings.)

      * fill() recognizes a special kind of substitution
        of the form `$*{name}`.

        Use this to paste in, and automatically indent, multiple lines.
        (Mnemonic: The `*` is for "multiple lines").

        A `$*` substitution must appear by itself on a line, with optional
        preceding indentation (spaces only). The whole line is replaced by the
        corresponding keyword argument, indented appropriately.  If the
        argument is an empty string, no output is generated, not even a blank
        line.
    """

    t, argModList = compile_fill_template(template)
    # Now apply argModList to args
    for name, modified_name, depth in argModList:
        if not (args[name] == "" or args[name].endswith("\n")):
            raise ValueError(
                "Argument %s with value %r is missing a newline" % (name, args[name])
            )
        args[modified_name] = indent(args[name], depth)

    return t.substitute(args)


class CGThing:
    """
    Abstract base class for things that spit out code.
    """

    def __init__(self):
        pass  # Nothing for now

    def declare(self):
        """Produce code for a header file."""
        assert False  # Override me!

    def define(self):
        """Produce code for a cpp file."""
        assert False  # Override me!

    def deps(self):
        """Produce the deps for a pp file"""
        assert False  # Override me!


class CGStringTable(CGThing):
    """
    Generate a function accessor for a WebIDL string table, using the existing
    concatenated names string and mapping indexes to offsets in that string:

    const char *accessorName(unsigned int index) {
      static const uint16_t offsets = { ... };
      return BindingName(offsets[index]);
    }

    This is more efficient than the more natural:

    const char *table[] = {
      ...
    };

    The uint16_t offsets are smaller than the pointer equivalents, and the
    concatenated string requires no runtime relocations.
    """

    def __init__(self, accessorName, strings, static=False):
        CGThing.__init__(self)
        self.accessorName = accessorName
        self.strings = strings
        self.static = static

    def declare(self):
        if self.static:
            return ""
        return "const char *%s(unsigned int aIndex);\n" % self.accessorName

    def define(self):
        offsets = []
        for s in self.strings:
            offsets.append(BindingNamesOffsetEnum(s))
        return fill(
            """
            ${static}const char *${name}(unsigned int aIndex)
            {
              static const BindingNamesOffset offsets[] = {
                $*{offsets}
              };
              return BindingName(offsets[aIndex]);
            }
            """,
            static="static " if self.static else "",
            name=self.accessorName,
            offsets="".join("BindingNamesOffset::%s,\n" % o for o in offsets),
        )


class CGNativePropertyHooks(CGThing):
    """
    Generate a NativePropertyHooks for a given descriptor
    """

    def __init__(self, descriptor, properties):
        CGThing.__init__(self)
        assert descriptor.wantsXrays
        self.descriptor = descriptor
        self.properties = properties

    def declare(self):
        return ""

    def define(self):
        if (
            self.descriptor.concrete
            and self.descriptor.proxy
            and not self.descriptor.isMaybeCrossOriginObject()
        ):
            if self.descriptor.needsXrayNamedDeleterHook():
                deleteNamedProperty = "DeleteNamedProperty"
            else:
                deleteNamedProperty = "nullptr"
            namedOrIndexed = fill(
                """
                const NativeNamedOrIndexedPropertyHooks sNativeNamedOrIndexedPropertyHooks = {
                  binding_detail::ResolveOwnProperty,
                  binding_detail::EnumerateOwnProperties,
                  ${deleteNamedProperty}
                };
                """,
                deleteNamedProperty=deleteNamedProperty,
            )
            namedOrIndexedPointer = "&sNativeNamedOrIndexedPropertyHooks"
        elif self.descriptor.needsXrayResolveHooks():
            namedOrIndexed = dedent(
                """
                const NativeNamedOrIndexedPropertyHooks sNativeNamedOrIndexedPropertyHooks = {
                  ResolveOwnPropertyViaResolve,
                  EnumerateOwnPropertiesViaGetOwnPropertyNames,
                  nullptr
                };
                """
            )
            namedOrIndexedPointer = "&sNativeNamedOrIndexedPropertyHooks"
        else:
            namedOrIndexed = ""
            namedOrIndexedPointer = "nullptr"
        if self.properties.hasNonChromeOnly():
            regular = "sNativeProperties.Upcast()"
        else:
            regular = "nullptr"
        if self.properties.hasChromeOnly():
            chrome = "sChromeOnlyNativeProperties.Upcast()"
        else:
            chrome = "nullptr"
        constructorID = "constructors::id::"
        if self.descriptor.interface.hasInterfaceObject():
            constructorID += self.descriptor.name
        else:
            constructorID += "_ID_Count"
        prototypeID = "prototypes::id::"
        if self.descriptor.interface.hasInterfacePrototypeObject():
            prototypeID += self.descriptor.name
        else:
            prototypeID += "_ID_Count"

        if self.descriptor.wantsXrayExpandoClass:
            expandoClass = "&sXrayExpandoObjectClass"
        else:
            expandoClass = "&DefaultXrayExpandoObjectClass"

        return namedOrIndexed + fill(
            """
            bool sNativePropertiesInited = false;
            const NativePropertyHooks sNativePropertyHooks = {
              ${namedOrIndexedPointer},
              { ${regular}, ${chrome}, &sNativePropertiesInited },
              ${prototypeID},
              ${constructorID},
              ${expandoClass}
            };
            """,
            namedOrIndexedPointer=namedOrIndexedPointer,
            regular=regular,
            chrome=chrome,
            prototypeID=prototypeID,
            constructorID=constructorID,
            expandoClass=expandoClass,
        )


def NativePropertyHooks(descriptor):
    return (
        "&sEmptyNativePropertyHooks"
        if not descriptor.wantsXrays
        else "&sNativePropertyHooks"
    )


def DOMClass(descriptor):
    protoList = ["prototypes::id::" + proto for proto in descriptor.prototypeNameChain]
    # Pad out the list to the right length with _ID_Count so we
    # guarantee that all the lists are the same length.  _ID_Count
    # is never the ID of any prototype, so it's safe to use as
    # padding.
    protoList.extend(
        ["prototypes::id::_ID_Count"]
        * (descriptor.config.maxProtoChainLength - len(protoList))
    )

    if descriptor.interface.isSerializable():
        serializer = "Serialize"
    else:
        serializer = "nullptr"

    if wantsGetWrapperCache(descriptor):
        wrapperCacheGetter = GETWRAPPERCACHE_HOOK_NAME
    else:
        wrapperCacheGetter = "nullptr"

    if descriptor.hasOrdinaryObjectPrototype():
        getProto = "JS::GetRealmObjectPrototypeHandle"
    else:
        getProto = "GetProtoObjectHandle"

    return fill(
        """
          { ${protoChain} },
          std::is_base_of_v<nsISupports, ${nativeType}>,
          ${hooks},
          FindAssociatedGlobalForNative<${nativeType}>::Get,
          ${getProto},
          GetCCParticipant<${nativeType}>::Get(),
          ${serializer},
          ${wrapperCacheGetter}
        """,
        protoChain=", ".join(protoList),
        nativeType=descriptor.nativeType,
        hooks=NativePropertyHooks(descriptor),
        serializer=serializer,
        wrapperCacheGetter=wrapperCacheGetter,
        getProto=getProto,
    )


def InstanceReservedSlots(descriptor):
    slots = INSTANCE_RESERVED_SLOTS + descriptor.interface.totalMembersInSlots
    if descriptor.isMaybeCrossOriginObject():
        # We need a slot for the cross-origin holder too.
        if descriptor.interface.hasChildInterfaces():
            raise TypeError(
                "We don't support non-leaf cross-origin interfaces "
                "like %s" % descriptor.interface.identifier.name
            )
        slots += 1
    return slots


class CGDOMJSClass(CGThing):
    """
    Generate a DOMJSClass for a given descriptor
    """

    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        return ""

    def define(self):
        callHook = (
            LEGACYCALLER_HOOK_NAME
            if self.descriptor.operations["LegacyCaller"]
            else "nullptr"
        )
        objectMovedHook = (
            OBJECT_MOVED_HOOK_NAME if self.descriptor.wrapperCache else "nullptr"
        )
        slotCount = InstanceReservedSlots(self.descriptor)
        classFlags = "JSCLASS_IS_DOMJSCLASS | JSCLASS_FOREGROUND_FINALIZE | "
        if self.descriptor.isGlobal():
            classFlags += (
                "JSCLASS_DOM_GLOBAL | JSCLASS_GLOBAL_FLAGS_WITH_SLOTS(DOM_GLOBAL_SLOTS)"
            )
            traceHook = "JS_GlobalObjectTraceHook"
            reservedSlots = "JSCLASS_GLOBAL_APPLICATION_SLOTS"
        else:
            classFlags += "JSCLASS_HAS_RESERVED_SLOTS(%d)" % slotCount
            iface = getReflectedHTMLAttributesIface(self.descriptor)
            if iface:
                traceHook = (
                    "%s::ReflectedHTMLAttributeSlots::Trace"
                    % toBindingNamespace(iface.identifier.name)
                )
            else:
                traceHook = "nullptr"
            reservedSlots = slotCount
        if self.descriptor.interface.hasProbablyShortLivingWrapper():
            if not self.descriptor.wrapperCache:
                raise TypeError(
                    "Need a wrapper cache to support nursery "
                    "allocation of DOM objects"
                )
            classFlags += " | JSCLASS_SKIP_NURSERY_FINALIZE"

        if self.descriptor.interface.getExtendedAttribute("NeedResolve"):
            resolveHook = RESOLVE_HOOK_NAME
            mayResolveHook = MAY_RESOLVE_HOOK_NAME
            newEnumerateHook = NEW_ENUMERATE_HOOK_NAME
        elif self.descriptor.isGlobal():
            resolveHook = "mozilla::dom::ResolveGlobal"
            mayResolveHook = "mozilla::dom::MayResolveGlobal"
            newEnumerateHook = "mozilla::dom::EnumerateGlobal"
        else:
            resolveHook = "nullptr"
            mayResolveHook = "nullptr"
            newEnumerateHook = "nullptr"

        return fill(
            """
            static const JSClassOps sClassOps = {
              ${addProperty}, /* addProperty */
              nullptr,               /* delProperty */
              nullptr,               /* enumerate */
              ${newEnumerate}, /* newEnumerate */
              ${resolve}, /* resolve */
              ${mayResolve}, /* mayResolve */
              ${finalize}, /* finalize */
              ${call}, /* call */
              nullptr,               /* construct */
              ${trace}, /* trace */
            };

            static const js::ClassExtension sClassExtension = {
              ${objectMoved} /* objectMovedOp */
            };

            static const DOMJSClass sClass = {
              { "${name}",
                ${flags},
                &sClassOps,
                JS_NULL_CLASS_SPEC,
                &sClassExtension,
                JS_NULL_OBJECT_OPS
              },
              $*{descriptor}
            };
            static_assert(${instanceReservedSlots} == DOM_INSTANCE_RESERVED_SLOTS,
                          "Must have the right minimal number of reserved slots.");
            static_assert(${reservedSlots} >= ${slotCount},
                          "Must have enough reserved slots.");
            """,
            name=self.descriptor.interface.getClassName(),
            flags=classFlags,
            addProperty=(
                ADDPROPERTY_HOOK_NAME
                if wantsAddProperty(self.descriptor)
                else "nullptr"
            ),
            newEnumerate=newEnumerateHook,
            resolve=resolveHook,
            mayResolve=mayResolveHook,
            finalize=FINALIZE_HOOK_NAME,
            call=callHook,
            trace=traceHook,
            objectMoved=objectMovedHook,
            descriptor=DOMClass(self.descriptor),
            instanceReservedSlots=INSTANCE_RESERVED_SLOTS,
            reservedSlots=reservedSlots,
            slotCount=slotCount,
        )


class CGDOMProxyJSClass(CGThing):
    """
    Generate a DOMJSClass for a given proxy descriptor
    """

    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        return ""

    def define(self):
        slotCount = InstanceReservedSlots(self.descriptor)
        # We need one reserved slot (DOM_OBJECT_SLOT).
        flags = ["JSCLASS_IS_DOMJSCLASS", "JSCLASS_HAS_RESERVED_SLOTS(%d)" % slotCount]
        # We don't use an IDL annotation for JSCLASS_EMULATES_UNDEFINED because
        # we don't want people ever adding that to any interface other than
        # HTMLAllCollection.  So just hardcode it here.
        if self.descriptor.interface.identifier.name == "HTMLAllCollection":
            flags.append("JSCLASS_EMULATES_UNDEFINED")
        return fill(
            """
            static const DOMJSClass sClass = {
              PROXY_CLASS_DEF("${name}",
                              ${flags}),
              $*{descriptor}
            };
            """,
            name=self.descriptor.interface.identifier.name,
            flags=" | ".join(flags),
            descriptor=DOMClass(self.descriptor),
        )


class CGXrayExpandoJSClass(CGThing):
    """
    Generate a JSClass for an Xray expando object.  This is only
    needed if we have members in slots (for [Cached] or [StoreInSlot]
    stuff).
    """

    def __init__(self, descriptor):
        assert descriptor.interface.totalMembersInSlots != 0
        assert descriptor.wantsXrays
        assert descriptor.wantsXrayExpandoClass
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        return ""

    def define(self):
        iface = getReflectedHTMLAttributesIface(self.descriptor)
        if iface:
            ops = (
                "&%s::ReflectedHTMLAttributeSlots::sXrayExpandoObjectClassOps"
                % toBindingNamespace(iface.identifier.name)
            )
        else:
            ops = "&xpc::XrayExpandoObjectClassOps"
        return fill(
            """
            // This may allocate too many slots, because we only really need
            // slots for our non-interface-typed members that we cache.  But
            // allocating slots only for those would make the slot index
            // computations much more complicated, so let's do this the simple
            // way for now.
            DEFINE_XRAY_EXPANDO_CLASS_WITH_OPS(static, sXrayExpandoObjectClass, ${memberSlots},
                                               ${ops});
            """,
            memberSlots=self.descriptor.interface.totalMembersInSlots,
            ops=ops,
        )


def PrototypeIDAndDepth(descriptor):
    prototypeID = "prototypes::id::"
    if descriptor.interface.hasInterfacePrototypeObject():
        prototypeID += descriptor.interface.identifier.name
        depth = "PrototypeTraits<%s>::Depth" % prototypeID
    else:
        prototypeID += "_ID_Count"
        depth = "0"
    return (prototypeID, depth)


def InterfacePrototypeObjectProtoGetter(descriptor):
    """
    Returns a tuple with two elements:

        1) The name of the function to call to get the prototype to use for the
           interface prototype object as a JSObject*.

        2) The name of the function to call to get the prototype to use for the
           interface prototype object as a JS::Handle<JSObject*> or None if no
           such function exists.
    """
    parentProtoName = descriptor.parentPrototypeName
    if descriptor.hasNamedPropertiesObject:
        protoGetter = "GetNamedPropertiesObject"
        protoHandleGetter = None
    elif parentProtoName is None:
        protoHandleGetter = None
        if descriptor.interface.getExtendedAttribute("ExceptionClass"):
            protoGetter = "JS::GetRealmErrorPrototype"
        elif descriptor.interface.isIteratorInterface():
            protoGetter = "JS::GetRealmIteratorPrototype"
        elif descriptor.interface.isAsyncIteratorInterface():
            protoGetter = "JS::GetRealmAsyncIteratorPrototype"
        else:
            protoGetter = "JS::GetRealmObjectPrototype"
            protoHandleGetter = "JS::GetRealmObjectPrototypeHandle"
    else:
        prefix = toBindingNamespace(parentProtoName)
        protoGetter = prefix + "::GetProtoObject"
        protoHandleGetter = prefix + "::GetProtoObjectHandle"

    return (protoGetter, protoHandleGetter)


class CGPrototypeJSClass(CGThing):
    def __init__(self, descriptor, properties):
        CGThing.__init__(self)
        self.descriptor = descriptor
        self.properties = properties

    def declare(self):
        # We're purely for internal consumption
        return ""

    def define(self):
        prototypeID, depth = PrototypeIDAndDepth(self.descriptor)
        slotCount = "DOM_INTERFACE_PROTO_SLOTS_BASE"
        # Globals handle unforgeables directly in Wrap() instead of
        # via a holder.
        if (
            self.descriptor.hasLegacyUnforgeableMembers
            and not self.descriptor.isGlobal()
        ):
            slotCount += (
                " + 1 /* slot for the JSObject holding the unforgeable properties */"
            )
        (protoGetter, _) = InterfacePrototypeObjectProtoGetter(self.descriptor)
        type = (
            "eGlobalInterfacePrototype"
            if self.descriptor.isGlobal()
            else "eInterfacePrototype"
        )
        return fill(
            """
            static const DOMIfaceAndProtoJSClass sPrototypeClass = {
              {
                "${name}Prototype",
                JSCLASS_IS_DOMIFACEANDPROTOJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(${slotCount}),
                JS_NULL_CLASS_OPS,
                JS_NULL_CLASS_SPEC,
                JS_NULL_CLASS_EXT,
                JS_NULL_OBJECT_OPS
              },
              ${type},
              ${prototypeID},
              ${depth},
              ${hooks},
              ${protoGetter}
            };
            """,
            name=self.descriptor.interface.getClassName(),
            slotCount=slotCount,
            type=type,
            hooks=NativePropertyHooks(self.descriptor),
            prototypeID=prototypeID,
            depth=depth,
            protoGetter=protoGetter,
        )


def InterfaceObjectProtoGetter(descriptor):
    """
    Returns the name of the function to call to get the prototype to use for the
    interface object's prototype as a JS::Handle<JSObject*>.
    """
    assert not descriptor.interface.isNamespace()
    parentInterface = descriptor.interface.parent
    if parentInterface:
        parentIfaceName = parentInterface.identifier.name
        parentDesc = descriptor.getDescriptor(parentIfaceName)
        prefix = toBindingNamespace(parentDesc.name)
        protoHandleGetter = prefix + "::GetConstructorObjectHandle"
    else:
        protoHandleGetter = "JS::GetRealmFunctionPrototypeHandle"
    return protoHandleGetter


class CGNamespaceObjectJSClass(CGThing):
    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        # We're purely for internal consumption
        return ""

    def define(self):
        classString = self.descriptor.interface.getExtendedAttribute("ClassString")
        if classString is None:
            classString = self.descriptor.interface.identifier.name
        else:
            classString = classString[0]
        return fill(
            """
            static const DOMIfaceAndProtoJSClass sNamespaceObjectClass = {
              {
                "${classString}",
                JSCLASS_IS_DOMIFACEANDPROTOJSCLASS,
                JS_NULL_CLASS_OPS,
                JS_NULL_CLASS_SPEC,
                JS_NULL_CLASS_EXT,
                JS_NULL_OBJECT_OPS
              },
              eNamespace,
              prototypes::id::_ID_Count,
              0,
              ${hooks},
              // This isn't strictly following the spec (see
              // https://console.spec.whatwg.org/#ref-for-dfn-namespace-object),
              // but should be ok for Xrays.
              JS::GetRealmObjectPrototype
            };
            """,
            classString=classString,
            hooks=NativePropertyHooks(self.descriptor),
        )


class CGInterfaceObjectInfo(CGThing):
    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor

    def declare(self):
        # We're purely for internal consumption
        return ""

    def define(self):
        if self.descriptor.interface.ctor():
            ctorname = CONSTRUCT_HOOK_NAME
            constructorArgs = methodLength(self.descriptor.interface.ctor())
        else:
            ctorname = "ThrowingConstructor"
            constructorArgs = 0
        constructorName = self.descriptor.interface.getClassName()
        wantsIsInstance = self.descriptor.interface.hasInterfacePrototypeObject()

        prototypeID, depth = PrototypeIDAndDepth(self.descriptor)
        protoHandleGetter = InterfaceObjectProtoGetter(self.descriptor)

        return fill(
            """
            static const DOMInterfaceInfo sInterfaceObjectInfo = {
              { ${ctorname}, ${hooks} },
              ${protoHandleGetter},
              ${depth},
              ${prototypeID},
              ${wantsIsInstance},
              ${constructorArgs},
              "${constructorName}",
            };
            """,
            ctorname=ctorname,
            hooks=NativePropertyHooks(self.descriptor),
            protoHandleGetter=protoHandleGetter,
            depth=depth,
            prototypeID=prototypeID,
            wantsIsInstance=toStringBool(wantsIsInstance),
            constructorArgs=constructorArgs,
            constructorName=constructorName,
        )


class CGList(CGThing):
    """
    Generate code for a list of GCThings.  Just concatenates them together, with
    an optional joiner string.  "\n" is a common joiner.
    """

    def __init__(self, children, joiner=""):
        CGThing.__init__(self)
        # Make a copy of the kids into a list, because if someone passes in a
        # generator we won't be able to both declare and define ourselves, or
        # define ourselves more than once!
        self.children = list(children)
        self.joiner = joiner

    def append(self, child):
        self.children.append(child)

    def prepend(self, child):
        self.children.insert(0, child)

    def extend(self, kids):
        self.children.extend(kids)

    def join(self, iterable):
        return self.joiner.join(s for s in iterable if len(s) > 0)

    def declare(self):
        return self.join(
            child.declare() for child in self.children if child is not None
        )

    def define(self):
        return self.join(child.define() for child in self.children if child is not None)

    def deps(self):
        deps = set()
        for child in self.children:
            if child is None:
                continue
            deps = deps.union(child.deps())
        return deps

    def __len__(self):
        return len(self.children)


class CGGeneric(CGThing):
    """
    A class that spits out a fixed string into the codegen.  Can spit out a
    separate string for the declaration too.
    """

    def __init__(self, define="", declare=""):
        self.declareText = declare
        self.defineText = define

    def declare(self):
        return self.declareText

    def define(self):
        return self.defineText

    def deps(self):
        return set()


class CGIndenter(CGThing):
    """
    A class that takes another CGThing and generates code that indents that
    CGThing by some number of spaces.  The default indent is two spaces.
    """

    def __init__(self, child, indentLevel=2, declareOnly=False):
        assert isinstance(child, CGThing)
        CGThing.__init__(self)
        self.child = child
        self.indentLevel = indentLevel
        self.declareOnly = declareOnly

    def declare(self):
        return indent(self.child.declare(), self.indentLevel)

    def define(self):
        defn = self.child.define()
        if self.declareOnly:
            return defn
        else:
            return indent(defn, self.indentLevel)


class CGWrapper(CGThing):
    """
    Generic CGThing that wraps other CGThings with pre and post text.
    """

    def __init__(
        self,
        child,
        pre="",
        post="",
        declarePre=None,
        declarePost=None,
        definePre=None,
        definePost=None,
        declareOnly=False,
        defineOnly=False,
        reindent=False,
    ):
        CGThing.__init__(self)
        self.child = child
        self.declarePre = declarePre or pre
        self.declarePost = declarePost or post
        self.definePre = definePre or pre
        self.definePost = definePost or post
        self.declareOnly = declareOnly
        self.defineOnly = defineOnly
        self.reindent = reindent

    def declare(self):
        if self.defineOnly:
            return ""
        decl = self.child.declare()
        if self.reindent:
            decl = self.reindentString(decl, self.declarePre)
        return self.declarePre + decl + self.declarePost

    def define(self):
        if self.declareOnly:
            return ""
        defn = self.child.define()
        if self.reindent:
            defn = self.reindentString(defn, self.definePre)
        return self.definePre + defn + self.definePost

    @staticmethod
    def reindentString(stringToIndent, widthString):
        # We don't use lineStartDetector because we don't want to
        # insert whitespace at the beginning of our _first_ line.
        # Use the length of the last line of width string, in case
        # it is a multiline string.
        lastLineWidth = len(widthString.splitlines()[-1])
        return stripTrailingWhitespace(
            stringToIndent.replace("\n", "\n" + (" " * lastLineWidth))
        )

    def deps(self):
        return self.child.deps()


class CGIfWrapper(CGList):
    def __init__(self, child, condition):
        CGList.__init__(
            self,
            [
                CGWrapper(
                    CGGeneric(condition), pre="if (", post=") {\n", reindent=True
                ),
                CGIndenter(child),
                CGGeneric("}\n"),
            ],
        )


class CGIfElseWrapper(CGList):
    def __init__(self, condition, ifTrue, ifFalse):
        CGList.__init__(
            self,
            [
                CGWrapper(
                    CGGeneric(condition), pre="if (", post=") {\n", reindent=True
                ),
                CGIndenter(ifTrue),
                CGGeneric("} else {\n"),
                CGIndenter(ifFalse),
                CGGeneric("}\n"),
            ],
        )


class CGElseChain(CGThing):
    """
    Concatenate if statements in an if-else-if-else chain.
    """

    def __init__(self, children):
        self.children = [c for c in children if c is not None]

    def declare(self):
        assert False

    def define(self):
        if not self.children:
            return ""
        s = self.children[0].define()
        assert s.endswith("\n")
        for child in self.children[1:]:
            code = child.define()
            assert code.startswith("if") or code.startswith("{")
            assert code.endswith("\n")
            s = s.rstrip() + " else " + code
        return s


class CGTemplatedType(CGWrapper):
    def __init__(self, templateName, child, isConst=False, isReference=False):
        if isinstance(child, list):
            child = CGList(child, ", ")
        const = "const " if isConst else ""
        pre = "%s%s<" % (const, templateName)
        ref = "&" if isReference else ""
        post = ">%s" % ref
        CGWrapper.__init__(self, child, pre=pre, post=post)


class CGNamespace(CGThing):
    """
    Generates namespace block that wraps other CGThings.
    """

    def __init__(self, namespace, child):
        CGThing.__init__(self)
        self.child = child
        self.pre = "namespace %s {\n" % namespace
        self.post = "} // namespace %s\n" % namespace

    def declare(self):
        decl = self.child.declare()
        if len(decl.strip()) == 0:
            return ""
        return self.pre + decl + self.post

    def define(self):
        defn = self.child.define()
        if len(defn.strip()) == 0:
            return ""
        return self.pre + defn + self.post

    def deps(self):
        return self.child.deps()

    @staticmethod
    def build(namespaces, child):
        """
        Static helper method to build multiple wrapped namespaces.
        """
        if not namespaces:
            return CGWrapper(child)
        return CGNamespace("::".join(namespaces), child)


class CGIncludeGuard(CGWrapper):
    """
    Generates include guards for a header.
    """

    def __init__(self, prefix, child):
        """|prefix| is the filename without the extension."""
        define = "DOM_%s_H_" % prefix.upper()
        CGWrapper.__init__(
            self,
            child,
            declarePre="#ifndef %s\n#define %s\n\n" % (define, define),
            declarePost="\n#endif // %s\n" % define,
        )


class CGHeaders(CGWrapper):
    """
    Generates the appropriate include statements.
    """

    def __init__(
        self,
        descriptors,
        dictionaries,
        callbacks,
        callbackDescriptors,
        declareIncludes,
        defineIncludes,
        prefix,
        child,
        config=None,
        jsImplementedDescriptors=[],
    ):
        """
        Builds a set of includes to cover |descriptors|.

        Also includes the files in |declareIncludes| in the header
        file and the files in |defineIncludes| in the .cpp.

        |prefix| contains the basename of the file that we generate include
        statements for.
        """

        # Determine the filenames for which we need headers.
        interfaceDeps = [d.interface for d in descriptors]
        ancestors = []
        for iface in interfaceDeps:
            if iface.parent:
                # We're going to need our parent's prototype, to use as the
                # prototype of our prototype object.
                ancestors.append(iface.parent)
                # And if we have an interface object, we'll need the nearest
                # ancestor with an interface object too, so we can use its
                # interface object as the proto of our interface object.
                if iface.hasInterfaceObject():
                    parent = iface.parent
                    while parent and not parent.hasInterfaceObject():
                        parent = parent.parent
                    if parent:
                        ancestors.append(parent)
        interfaceDeps.extend(ancestors)

        # Include parent interface headers needed for default toJSON code.
        jsonInterfaceParents = []
        for desc in descriptors:
            if not desc.hasDefaultToJSON:
                continue
            parent = desc.interface.parent
            while parent:
                parentDesc = desc.getDescriptor(parent.identifier.name)
                if parentDesc.hasDefaultToJSON:
                    jsonInterfaceParents.append(parentDesc.interface)
                parent = parent.parent
        interfaceDeps.extend(jsonInterfaceParents)

        bindingIncludes = set(self.getDeclarationFilename(d) for d in interfaceDeps)

        # Grab all the implementation declaration files we need.
        implementationIncludes = set(
            d.headerFile for d in descriptors if d.needsHeaderInclude()
        )

        # Now find all the things we'll need as arguments because we
        # need to wrap or unwrap them.
        bindingHeaders = set()
        declareIncludes = set(declareIncludes)

        def addHeadersForType(typeAndPossibleOriginType):
            """
            Add the relevant headers for this type.  We use its origin type, if
            passed, to decide what to do with interface types.
            """
            t, originType = typeAndPossibleOriginType
            isFromDictionary = originType and originType.isDictionary()
            isFromCallback = originType and originType.isCallback()
            # Dictionaries have members that need to be actually
            # declared, not just forward-declared.
            # Callbacks have nullable union arguments that need to be actually
            # declared, not just forward-declared.
            if isFromDictionary:
                headerSet = declareIncludes
            elif isFromCallback and t.nullable() and t.isUnion():
                headerSet = declareIncludes
            else:
                headerSet = bindingHeaders
            # Strip off outer layers and add headers they might require.  (This
            # is conservative: only nullable non-pointer types need Nullable.h;
            # only sequences or observable arrays outside unions need
            # ForOfIterator.h; only functions that return, and attributes that
            # are, sequences or observable arrays in interfaces need Array.h, &c.)
            unrolled = t
            while True:
                if idlTypeNeedsCallContext(unrolled):
                    bindingHeaders.add("mozilla/dom/BindingCallContext.h")
                if unrolled.nullable():
                    headerSet.add("mozilla/dom/Nullable.h")
                elif unrolled.isSequence() or unrolled.isObservableArray():
                    bindingHeaders.add("js/Array.h")
                    bindingHeaders.add("js/ForOfIterator.h")
                    if unrolled.isObservableArray():
                        bindingHeaders.add("mozilla/dom/ObservableArrayProxyHandler.h")
                else:
                    break
                unrolled = unrolled.inner
            if unrolled.isUnion():
                headerSet.add(self.getUnionDeclarationFilename(config, unrolled))
                for t in unrolled.flatMemberTypes:
                    addHeadersForType((t, None))
            elif unrolled.isPromise():
                # See comment in the isInterface() case for why we add
                # Promise.h to headerSet, not bindingHeaders.
                headerSet.add("mozilla/dom/Promise.h")
                # We need ToJSValue to do the Promise to JS conversion.
                bindingHeaders.add("mozilla/dom/ToJSValue.h")
            elif unrolled.isInterface():
                if unrolled.isSpiderMonkeyInterface():
                    bindingHeaders.add("jsfriendapi.h")
                    if jsImplementedDescriptors:
                        # Since we can't forward-declare typed array types
                        # (because they're typedefs), we have to go ahead and
                        # just include their header if we need to have functions
                        # taking references to them declared in that header.
                        headerSet = declareIncludes
                    headerSet.add("mozilla/dom/TypedArray.h")
                else:
                    try:
                        typeDesc = config.getDescriptor(unrolled.inner.identifier.name)
                    except NoSuchDescriptorError:
                        return
                    # Dictionaries with interface members rely on the
                    # actual class definition of that interface member
                    # being visible in the binding header, because they
                    # store them in RefPtr and have inline
                    # constructors/destructors.
                    #
                    # XXXbz maybe dictionaries with interface members
                    # should just have out-of-line constructors and
                    # destructors?
                    headerSet.add(typeDesc.headerFile)
            elif unrolled.isDictionary():
                headerSet.add(self.getDeclarationFilename(unrolled.inner))
                # And if it needs rooting, we need RootedDictionary too
                if typeNeedsRooting(unrolled):
                    headerSet.add("mozilla/dom/RootedDictionary.h")
            elif unrolled.isCallback():
                headerSet.add(self.getDeclarationFilename(unrolled.callback))
            elif unrolled.isFloat() and not unrolled.isUnrestricted():
                # Restricted floats are tested for finiteness
                bindingHeaders.add("mozilla/FloatingPoint.h")
                bindingHeaders.add("mozilla/dom/PrimitiveConversions.h")
            elif unrolled.isEnum():
                filename = self.getDeclarationFilename(unrolled.inner)
                declareIncludes.add(filename)
            elif unrolled.isPrimitive():
                bindingHeaders.add("mozilla/dom/PrimitiveConversions.h")
            elif unrolled.isRecord():
                if isFromDictionary or jsImplementedDescriptors:
                    declareIncludes.add("mozilla/dom/Record.h")
                else:
                    bindingHeaders.add("mozilla/dom/Record.h")
                # Also add headers for the type the record is
                # parametrized over, if needed.
                addHeadersForType((t.inner, originType if isFromDictionary else None))

        for t in getAllTypes(
            descriptors + callbackDescriptors, dictionaries, callbacks
        ):
            addHeadersForType(t)

        def addHeaderForFunc(func, desc):
            if func is None:
                return
            # Include the right class header, which we can only do
            # if this is a class member function.
            if desc is not None and not desc.headerIsDefault:
                # An explicit header file was provided, assume that we know
                # what we're doing.
                return

            if "::" in func:
                # Strip out the function name and convert "::" to "/"
                bindingHeaders.add("/".join(func.split("::")[:-1]) + ".h")

        # Now for non-callback descriptors make sure we include any
        # headers needed by Func declarations and other things like that.
        for desc in descriptors:
            # If this is an iterator or an async iterator interface generated
            # for a separate iterable interface, skip generating type includes,
            # as we have what we need in IterableIterator.h
            if (
                desc.interface.isIteratorInterface()
                or desc.interface.isAsyncIteratorInterface()
            ):
                continue

            for m in desc.interface.members:
                addHeaderForFunc(PropertyDefiner.getStringAttr(m, "Func"), desc)
                staticTypeOverride = PropertyDefiner.getStringAttr(
                    m, "StaticClassOverride"
                )
                if staticTypeOverride:
                    bindingHeaders.add("/".join(staticTypeOverride.split("::")) + ".h")
            # getExtendedAttribute() returns a list, extract the entry.
            funcList = desc.interface.getExtendedAttribute("Func")
            if funcList is not None:
                addHeaderForFunc(funcList[0], desc)

            if desc.interface.maplikeOrSetlikeOrIterable:
                # We need ToJSValue.h for maplike/setlike type conversions
                bindingHeaders.add("mozilla/dom/ToJSValue.h")
                # Add headers for the key and value types of the
                # maplike/setlike/iterable, since they'll be needed for
                # convenience functions
                if desc.interface.maplikeOrSetlikeOrIterable.hasKeyType():
                    addHeadersForType(
                        (desc.interface.maplikeOrSetlikeOrIterable.keyType, None)
                    )
                if desc.interface.maplikeOrSetlikeOrIterable.hasValueType():
                    addHeadersForType(
                        (desc.interface.maplikeOrSetlikeOrIterable.valueType, None)
                    )

        for d in dictionaries:
            if d.parent:
                declareIncludes.add(self.getDeclarationFilename(d.parent))
            bindingHeaders.add(self.getDeclarationFilename(d))
            for m in d.members:
                addHeaderForFunc(PropertyDefiner.getStringAttr(m, "Func"), None)
            # No need to worry about Func on members of ancestors, because that
            # will happen automatically in whatever files those ancestors live
            # in.

        for c in callbacks:
            bindingHeaders.add(self.getDeclarationFilename(c))

        for c in callbackDescriptors:
            bindingHeaders.add(self.getDeclarationFilename(c.interface))

        if len(callbacks) != 0:
            # We need CallbackFunction to serve as our parent class
            declareIncludes.add("mozilla/dom/CallbackFunction.h")
            # And we need ToJSValue.h so we can wrap "this" objects
            declareIncludes.add("mozilla/dom/ToJSValue.h")

        if len(callbackDescriptors) != 0 or len(jsImplementedDescriptors) != 0:
            # We need CallbackInterface to serve as our parent class
            declareIncludes.add("mozilla/dom/CallbackInterface.h")
            # And we need ToJSValue.h so we can wrap "this" objects
            declareIncludes.add("mozilla/dom/ToJSValue.h")

        # Also need to include the headers for ancestors of
        # JS-implemented interfaces.
        for jsImplemented in jsImplementedDescriptors:
            jsParent = jsImplemented.interface.parent
            if jsParent:
                parentDesc = jsImplemented.getDescriptor(jsParent.identifier.name)
                declareIncludes.add(parentDesc.jsImplParentHeader)

        # Now make sure we're not trying to include the header from inside itself
        declareIncludes.discard(prefix + ".h")

        # Let the machinery do its thing.
        def _includeString(includes):
            def headerName(include):
                # System headers are specified inside angle brackets.
                if include.startswith("<"):
                    return include
                # Non-system headers need to be placed in quotes.
                return '"%s"' % include

            return "".join(["#include %s\n" % headerName(i) for i in includes]) + "\n"

        CGWrapper.__init__(
            self,
            child,
            declarePre=_includeString(sorted(declareIncludes)),
            definePre=_includeString(
                sorted(
                    set(defineIncludes)
                    | bindingIncludes
                    | bindingHeaders
                    | implementationIncludes
                )
            ),
        )

    @staticmethod
    def getDeclarationFilename(decl):
        # Use our local version of the header, not the exported one, so that
        # test bindings, which don't export, will work correctly.
        basename = os.path.basename(decl.filename)
        return basename.replace(".webidl", "Binding.h")

    @staticmethod
    def getUnionDeclarationFilename(config, unionType):
        assert unionType.isUnion()
        assert unionType.unroll() == unionType
        # If a union is "defined" in multiple files, it goes in UnionTypes.h.
        if len(config.filenamesPerUnion[unionType.name]) > 1:
            return "mozilla/dom/UnionTypes.h"
        # If a union is defined by a built-in typedef, it also goes in
        # UnionTypes.h.
        assert len(config.filenamesPerUnion[unionType.name]) == 1
        if "<unknown>" in config.filenamesPerUnion[unionType.name]:
            return "mozilla/dom/UnionTypes.h"
        return CGHeaders.getDeclarationFilename(unionType)


def SortedDictValues(d):
    """
    Returns a list of values from the dict sorted by key.
    """
    return [v for k, v in sorted(d.items())]


def UnionsForFile(config, webIDLFile):
    """
    Returns a list of union types for all union types that are only used in
    webIDLFile. If webIDLFile is None this will return the list of tuples for
    union types that are used in more than one WebIDL file.
    """
    return config.unionsPerFilename.get(webIDLFile, [])


def UnionTypes(unionTypes, config):
    """
    The unionTypes argument should be a list of union types. This is typically
    the list generated by UnionsForFile.

    Returns a tuple containing a set of header filenames to include in
    the header for the types in unionTypes, a set of header filenames to
    include in the implementation file for the types in unionTypes, a set
    of tuples containing a type declaration and a boolean if the type is a
    struct for member types of the union, a list of traverse methods,
    unlink methods and a list of union types. These last three lists only
    contain unique union types.
    """

    headers = set()
    implheaders = set()
    declarations = set()
    unionStructs = dict()
    traverseMethods = dict()
    unlinkMethods = dict()

    for t in unionTypes:
        name = str(t)
        if name not in unionStructs:
            unionStructs[name] = t

            def addHeadersForType(f):
                if f.nullable():
                    headers.add("mozilla/dom/Nullable.h")
                isSequence = f.isSequence()
                if isSequence:
                    # Dealing with sequences requires for-of-compatible
                    # iteration.
                    implheaders.add("js/ForOfIterator.h")
                    # Sequences can always throw "not an object" exceptions.
                    implheaders.add("mozilla/dom/BindingCallContext.h")
                    if typeNeedsRooting(f):
                        headers.add("mozilla/dom/RootedSequence.h")
                f = f.unroll()
                if idlTypeNeedsCallContext(f):
                    implheaders.add("mozilla/dom/BindingCallContext.h")
                if f.isPromise():
                    headers.add("mozilla/dom/Promise.h")
                    # We need ToJSValue to do the Promise to JS conversion.
                    headers.add("mozilla/dom/ToJSValue.h")
                elif f.isInterface():
                    if f.isSpiderMonkeyInterface():
                        headers.add("js/RootingAPI.h")
                        headers.add("js/Value.h")
                        headers.add("mozilla/dom/TypedArray.h")
                    else:
                        try:
                            typeDesc = config.getDescriptor(f.inner.identifier.name)
                        except NoSuchDescriptorError:
                            return
                        if typeDesc.interface.isCallback() or isSequence:
                            # Callback interfaces always use strong refs, so
                            # we need to include the right header to be able
                            # to Release() in our inlined code.
                            #
                            # Similarly, sequences always contain strong
                            # refs, so we'll need the header to handler
                            # those.
                            headers.add(typeDesc.headerFile)
                        elif typeDesc.interface.identifier.name == "WindowProxy":
                            # In UnionTypes.h we need to see the declaration of the
                            # WindowProxyHolder that we use to store the WindowProxy, so
                            # we have its sizeof and know how big to make our union.
                            headers.add(typeDesc.headerFile)
                        else:
                            declarations.add((typeDesc.nativeType, False))
                            implheaders.add(typeDesc.headerFile)
                elif f.isDictionary():
                    # For a dictionary, we need to see its declaration in
                    # UnionTypes.h so we have its sizeof and know how big to
                    # make our union.
                    headers.add(CGHeaders.getDeclarationFilename(f.inner))
                    # And if it needs rooting, we need RootedDictionary too
                    if typeNeedsRooting(f):
                        headers.add("mozilla/dom/RootedDictionary.h")
                elif f.isFloat() and not f.isUnrestricted():
                    # Restricted floats are tested for finiteness
                    implheaders.add("mozilla/FloatingPoint.h")
                    implheaders.add("mozilla/dom/PrimitiveConversions.h")
                elif f.isEnum():
                    # Need to see the actual definition of the enum,
                    # unfortunately.
                    headers.add(CGHeaders.getDeclarationFilename(f.inner))
                elif f.isPrimitive():
                    implheaders.add("mozilla/dom/PrimitiveConversions.h")
                elif f.isCallback():
                    # Callbacks always use strong refs, so we need to include
                    # the right header to be able to Release() in our inlined
                    # code.
                    headers.add(CGHeaders.getDeclarationFilename(f.callback))
                elif f.isRecord():
                    headers.add("mozilla/dom/Record.h")
                    # And add headers for the type we're parametrized over
                    addHeadersForType(f.inner)
                    # And if it needs rooting, we need RootedRecord too
                    if typeNeedsRooting(f):
                        headers.add("mozilla/dom/RootedRecord.h")

            implheaders.add(CGHeaders.getUnionDeclarationFilename(config, t))
            for f in t.flatMemberTypes:
                assert not f.nullable()
                addHeadersForType(f)

            if idlTypeNeedsCycleCollection(t):
                declarations.add(
                    ("mozilla::dom::%s" % CGUnionStruct.unionTypeName(t, True), False)
                )
                traverseMethods[name] = CGCycleCollectionTraverseForOwningUnionMethod(t)
                unlinkMethods[name] = CGCycleCollectionUnlinkForOwningUnionMethod(t)

    # The order of items in CGList is important.
    # Since the union structs friend the unlinkMethods, the forward-declaration
    # for these methods should come before the class declaration. Otherwise
    # some compilers treat the friend declaration as a forward-declaration in
    # the class scope.
    return (
        headers,
        implheaders,
        declarations,
        SortedDictValues(traverseMethods),
        SortedDictValues(unlinkMethods),
        SortedDictValues(unionStructs),
    )


class Argument:
    """
    A class for outputting the type and name of an argument
    """

    def __init__(self, argType, name, default=None):
        self.argType = argType
        self.name = name
        self.default = default

    def declare(self):
        string = self.argType + " " + self.name
        if self.default is not None:
            string += " = " + self.default
        return string

    def define(self):
        return self.argType + " " + self.name


class CGAbstractMethod(CGThing):
    """
    An abstract class for generating code for a method.  Subclasses
    should override definition_body to create the actual code.

    descriptor is the descriptor for the interface the method is associated with

    name is the name of the method as a string

    returnType is the IDLType of the return value

    args is a list of Argument objects

    inline should be True to generate an inline method, whose body is
    part of the declaration.

    alwaysInline should be True to generate an inline method annotated with
    MOZ_ALWAYS_INLINE.

    static should be True to generate a static method, which only has
    a definition.

    If templateArgs is not None it should be a list of strings containing
    template arguments, and the function will be templatized using those
    arguments.

    canRunScript should be True to generate a MOZ_CAN_RUN_SCRIPT annotation.

    signatureOnly should be True to only declare the signature (either in
                  the header, or if static is True in the cpp file).
    """

    def __init__(
        self,
        descriptor,
        name,
        returnType,
        args,
        inline=False,
        alwaysInline=False,
        static=False,
        templateArgs=None,
        canRunScript=False,
        signatureOnly=False,
    ):
        CGThing.__init__(self)
        self.descriptor = descriptor
        self.name = name
        self.returnType = returnType
        self.args = args
        self.inline = inline
        self.alwaysInline = alwaysInline
        self.static = static
        self.templateArgs = templateArgs
        self.canRunScript = canRunScript
        self.signatureOnly = signatureOnly

    def _argstring(self, declare):
        return ", ".join([a.declare() if declare else a.define() for a in self.args])

    def _template(self):
        if self.templateArgs is None:
            return ""
        return "template <%s>\n" % ", ".join(self.templateArgs)

    def _decorators(self):
        decorators = []
        if self.canRunScript:
            decorators.append("MOZ_CAN_RUN_SCRIPT")
        if self.alwaysInline:
            decorators.append("MOZ_ALWAYS_INLINE")
        elif self.inline:
            decorators.append("inline")
        if self.static:
            decorators.append("static")
        decorators.append(self.returnType)
        maybeNewline = " " if self.inline else "\n"
        return " ".join(decorators) + maybeNewline

    def signature(self):
        return "%s%s%s(%s);\n" % (
            self._template(),
            self._decorators(),
            self.name,
            self._argstring(True),
        )

    def declare(self):
        if self.static:
            return ""
        if self.inline:
            return self._define(True)
        return self.signature()

    def indent_body(self, body):
        """
        Indent the code returned by self.definition_body(). Most classes
        simply indent everything two spaces. This is here for
        CGRegisterProtos, which needs custom indentation.
        """
        return indent(body)

    def _define(self, fromDeclare=False):
        return (
            self.definition_prologue(fromDeclare)
            + self.indent_body(self.definition_body())
            + self.definition_epilogue()
        )

    def define(self):
        if self.signatureOnly:
            if self.static:
                # self.static makes us not output anything in the header, so output the signature here.
                return self.signature()
            return ""
        return "" if (self.inline and not self.static) else self._define()

    def definition_prologue(self, fromDeclare):
        error_reporting_label = self.error_reporting_label()
        if error_reporting_label:
            # We're going to want a BindingCallContext.  Rename our JSContext*
            # arg accordingly.
            i = 0
            while i < len(self.args):
                arg = self.args[i]
                if arg.argType == "JSContext*":
                    cxname = arg.name
                    self.args[i] = Argument(arg.argType, "cx_", arg.default)
                    break
                i += 1
            if i == len(self.args):
                raise TypeError("Must have a JSContext* to create a BindingCallContext")

        prologue = "%s%s%s(%s)\n{\n" % (
            self._template(),
            self._decorators(),
            self.name,
            self._argstring(fromDeclare),
        )
        if error_reporting_label:
            prologue += indent(
                fill(
                    """
                BindingCallContext ${cxname}(cx_, ${label});
                """,
                    cxname=cxname,
                    label=error_reporting_label,
                )
            )

        profiler_label = self.auto_profiler_label()
        if profiler_label:
            prologue += indent(profiler_label) + "\n"

        return prologue

    def definition_epilogue(self):
        return "}\n"

    def definition_body(self):
        assert False  # Override me!

    """
    Override this method to return a pair of (descriptive string, name of a
    JSContext* variable) in order to generate a profiler label for this method.
    """

    def auto_profiler_label(self):
        return None  # Override me!

    """
    Override this method to return a string to be used as the label for a
    BindingCallContext.  If this does not return None, one of the arguments of
    this method must be of type 'JSContext*'.  Its name will be replaced with
    'cx_' and a BindingCallContext named 'cx' will be instantiated with the
    given label.
    """

    def error_reporting_label(self):
        return None  # Override me!


class CGAbstractStaticMethod(CGAbstractMethod):
    """
    Abstract base class for codegen of implementation-only (no
    declaration) static methods.
    """

    def __init__(self, descriptor, name, returnType, args, canRunScript=False):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            name,
            returnType,
            args,
            inline=False,
            static=True,
            canRunScript=canRunScript,
        )


class CGAbstractClassHook(CGAbstractStaticMethod):
    """
    Meant for implementing JSClass hooks, like Finalize or Trace. Does very raw
    'this' unwrapping as it assumes that the unwrapped type is always known.
    """

    def __init__(self, descriptor, name, returnType, args):
        CGAbstractStaticMethod.__init__(self, descriptor, name, returnType, args)

    def definition_body_prologue(self):
        return "%s* self = UnwrapPossiblyNotInitializedDOMObject<%s>(obj);\n" % (
            self.descriptor.nativeType,
            self.descriptor.nativeType,
        )

    def definition_body(self):
        return self.definition_body_prologue() + self.generate_code()

    def generate_code(self):
        assert False  # Override me!


class CGAddPropertyHook(CGAbstractClassHook):
    """
    A hook for addProperty, used to preserve our wrapper from GC.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("JS::Handle<JS::Value>", "val"),
        ]
        CGAbstractClassHook.__init__(
            self, descriptor, ADDPROPERTY_HOOK_NAME, "bool", args
        )

    def generate_code(self):
        assert self.descriptor.wrapperCache
        # This hook is also called by TryPreserveWrapper on non-nsISupports
        # cycle collected objects, so if addProperty is ever changed to do
        # anything more or less than preserve the wrapper, TryPreserveWrapper
        # will need to be changed.
        return dedent(
            """
            // We don't want to preserve if we don't have a wrapper, and we
            // obviously can't preserve if we're not initialized.
            if (self && self->GetWrapperPreserveColor()) {
              PreserveWrapper(self);
            }
            return true;
            """
        )


class CGGetWrapperCacheHook(CGAbstractClassHook):
    """
    A hook for GetWrapperCache, used by HasReleasedWrapper to get the
    nsWrapperCache pointer for a non-nsISupports object.
    """

    def __init__(self, descriptor):
        args = [Argument("JS::Handle<JSObject*>", "obj")]
        CGAbstractClassHook.__init__(
            self, descriptor, GETWRAPPERCACHE_HOOK_NAME, "nsWrapperCache*", args
        )

    def generate_code(self):
        assert self.descriptor.wrapperCache
        return dedent(
            """
            return self;
            """
        )


class CGDefineHTMLAttributeSlots(CGThing):
    """
    Function to get the slots object for reflected HTML attributes that return
    a FrozenArray<Element> value.
    """

    def __init__(self, descriptor):
        self.descriptor = descriptor
        CGThing.__init__(self)

    def declare(self):
        atts = self.descriptor.interface.reflectedHTMLAttributesReturningFrozenArray
        return fill(
            """
            using ReflectedHTMLAttributeSlots = binding_detail::ReflectedHTMLAttributeSlots<${slotIndex}, ${xraySlotIndex}, ${arrayLength}>;
            """,
            slotIndex=reservedSlot(atts.slotIndex, False),
            xraySlotIndex=reservedSlot(atts.slotIndex, True),
            arrayLength=atts.totalMembersInSlots,
        )

    def define(self):
        return ""


def finalizeHook(descriptor, hookName, gcx, obj):
    finalize = "JS::SetReservedSlot(%s, DOM_OBJECT_SLOT, JS::UndefinedValue());\n" % obj
    if descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns"):
        finalize += fill(
            """
            // Either our proxy created an expando object or not.  If it did,
            // then we would have preserved ourselves, and hence if we're going
            // away so is our C++ object and we should reset its expando value.
            // It's possible that in this situation the C++ object's reflector
            // pointer has been nulled out, but if not it's pointing to us.  If
            // our proxy did _not_ create an expando object then it's possible
            // that we're no longer the reflector for our C++ object (and
            // incremental finalization is finally getting to us), and that in
            // the meantime the new reflector has created an expando object.
            // In that case we do NOT want to clear the expando pointer in the
            // C++ object.
            //
            // It's important to do this before we ClearWrapper, of course.
            JSObject* reflector = self->GetWrapperMaybeDead();
            if (!reflector || reflector == ${obj}) {
              self->mExpandoAndGeneration.expando = JS::UndefinedValue();
            }
            """,
            obj=obj,
        )
    for m in descriptor.interface.members:
        if m.isAttr() and m.type.isObservableArray():
            finalize += fill(
                """
                {
                  JS::Value val = JS::GetReservedSlot(obj, ${slot});
                  if (!val.isUndefined()) {
                    JSObject* obj = &val.toObject();
                    js::SetProxyReservedSlot(obj, OBSERVABLE_ARRAY_DOM_INTERFACE_SLOT, JS::UndefinedValue());
                  }
                }
                """,
                slot=memberReservedSlot(m, descriptor),
            )
    iface = getReflectedHTMLAttributesIface(descriptor)
    if iface:
        finalize += "%s::ReflectedHTMLAttributeSlots::Finalize(%s);\n" % (
            toBindingNamespace(iface.identifier.name),
            obj,
        )
    if descriptor.wrapperCache:
        finalize += "ClearWrapper(self, self, %s);\n" % obj
    if descriptor.isGlobal():
        finalize += "mozilla::dom::FinalizeGlobal(%s, %s);\n" % (gcx, obj)
    finalize += fill(
        """
        if (size_t mallocBytes = BindingJSObjectMallocBytes(self)) {
          JS::RemoveAssociatedMemory(${obj}, mallocBytes,
                                     JS::MemoryUse::DOMBinding);
        }
        """,
        obj=obj,
    )
    finalize += "AddForDeferredFinalization<%s>(self);\n" % descriptor.nativeType
    return CGIfWrapper(CGGeneric(finalize), "self")


class CGClassFinalizeHook(CGAbstractClassHook):
    """
    A hook for finalize, used to release our native object.
    """

    def __init__(self, descriptor):
        args = [Argument("JS::GCContext*", "gcx"), Argument("JSObject*", "obj")]
        CGAbstractClassHook.__init__(self, descriptor, FINALIZE_HOOK_NAME, "void", args)

    def generate_code(self):
        return finalizeHook(
            self.descriptor, self.name, self.args[0].name, self.args[1].name
        ).define()


def objectMovedHook(descriptor, hookName, obj, old):
    assert descriptor.wrapperCache
    return fill(
        """
        if (self) {
          UpdateWrapper(self, self, ${obj}, ${old});
        }

        return 0;
        """,
        obj=obj,
        old=old,
    )


class CGClassObjectMovedHook(CGAbstractClassHook):
    """
    A hook for objectMovedOp, used to update the wrapper cache when an object it
    is holding moves.
    """

    def __init__(self, descriptor):
        args = [Argument("JSObject*", "obj"), Argument("JSObject*", "old")]
        CGAbstractClassHook.__init__(
            self, descriptor, OBJECT_MOVED_HOOK_NAME, "size_t", args
        )

    def generate_code(self):
        return objectMovedHook(
            self.descriptor, self.name, self.args[0].name, self.args[1].name
        )


def JSNativeArguments():
    return [
        Argument("JSContext*", "cx"),
        Argument("unsigned", "argc"),
        Argument("JS::Value*", "vp"),
    ]


class CGClassConstructor(CGAbstractStaticMethod):
    """
    JS-visible constructor for our objects
    """

    def __init__(self, descriptor, ctor, name=CONSTRUCT_HOOK_NAME):
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", JSNativeArguments()
        )
        self._ctor = ctor

    def define(self):
        if not self._ctor:
            return ""
        return CGAbstractStaticMethod.define(self)

    def definition_body(self):
        return self.generate_code()

    def generate_code(self):
        if self._ctor.isHTMLConstructor():
            # We better have a prototype object.  Otherwise our proto
            # id won't make sense.
            assert self.descriptor.interface.hasInterfacePrototypeObject()
            # We also better have a constructor object, if this is
            # getting called!
            assert self.descriptor.interface.hasInterfaceObject()
            # We can't just pass null for the CreateInterfaceObjects callback,
            # because our newTarget might be in a different compartment, in
            # which case we'll need to look up constructor objects in that
            # compartment.
            return fill(
                """
                return HTMLConstructor(cx, argc, vp,
                                       constructors::id::${name},
                                       prototypes::id::${name},
                                       CreateInterfaceObjects);
                """,
                name=self.descriptor.name,
            )

        # If the interface is already SecureContext, notify getConditionList to skip that check,
        # because the constructor won't be exposed in non-secure contexts to start with.
        alreadySecureContext = self.descriptor.interface.getExtendedAttribute(
            "SecureContext"
        )

        # We want to throw if any of the conditions returned by getConditionList are false.
        conditionsCheck = ""
        rawConditions = getRawConditionList(
            self._ctor, "cx", "obj", alreadySecureContext
        )
        if len(rawConditions) > 0:
            notConditions = " ||\n".join("!" + cond for cond in rawConditions)
            failedCheckAction = CGGeneric("return ThrowingConstructor(cx, argc, vp);\n")
            conditionsCheck = (
                CGIfWrapper(failedCheckAction, notConditions).define() + "\n"
            )

        # Additionally, we want to throw if a caller does a bareword invocation
        # of a constructor without |new|.
        ctorName = GetConstructorNameForReporting(self.descriptor, self._ctor)

        preamble = fill(
            """
            JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
            JS::Rooted<JSObject*> obj(cx, &args.callee());
            $*{conditionsCheck}
            if (!args.isConstructing()) {
              return ThrowConstructorWithoutNew(cx, "${ctorName}");
            }

            JS::Rooted<JSObject*> desiredProto(cx);
            if (!GetDesiredProto(cx, args,
                                 prototypes::id::${name},
                                 CreateInterfaceObjects,
                                 &desiredProto)) {
              return false;
            }
            """,
            conditionsCheck=conditionsCheck,
            ctorName=ctorName,
            name=self.descriptor.name,
        )

        name = self._ctor.identifier.name
        nativeName = MakeNativeName(self.descriptor.binaryNameFor(name, True))
        callGenerator = CGMethodCall(
            nativeName, True, self.descriptor, self._ctor, isConstructor=True
        )
        return preamble + "\n" + callGenerator.define()

    def auto_profiler_label(self):
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${ctorName}", "constructor", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            ctorName=GetConstructorNameForReporting(self.descriptor, self._ctor),
        )

    def error_reporting_label(self):
        return CGSpecializedMethod.error_reporting_label_helper(
            self.descriptor, self._ctor, isConstructor=True
        )


def LegacyFactoryFunctionName(m):
    return "_" + m.identifier.name


class CGLegacyFactoryFunctions(CGThing):
    def __init__(self, descriptor):
        self.descriptor = descriptor
        CGThing.__init__(self)

    def declare(self):
        return ""

    def define(self):
        if len(self.descriptor.interface.legacyFactoryFunctions) == 0:
            return ""

        constructorID = "constructors::id::"
        if self.descriptor.interface.hasInterfaceObject():
            constructorID += self.descriptor.name
        else:
            constructorID += "_ID_Count"

        legacyFactoryFunctions = ""
        for n in self.descriptor.interface.legacyFactoryFunctions:
            legacyFactoryFunctions += (
                '{ "%s", { %s, &sLegacyFactoryFunctionNativePropertyHooks }, %i },\n'
                % (n.identifier.name, LegacyFactoryFunctionName(n), methodLength(n))
            )

        return fill(
            """
            bool sLegacyFactoryFunctionNativePropertiesInited = true;
            const NativePropertyHooks sLegacyFactoryFunctionNativePropertyHooks = {
                nullptr,
                { nullptr, nullptr, &sLegacyFactoryFunctionNativePropertiesInited },
                prototypes::id::${name},
                ${constructorID},
                nullptr
            };

            static const LegacyFactoryFunction legacyFactoryFunctions[] = {
              $*{legacyFactoryFunctions}
            };
            """,
            name=self.descriptor.name,
            constructorID=constructorID,
            legacyFactoryFunctions=legacyFactoryFunctions,
        )


def isChromeOnly(m):
    return m.getExtendedAttribute("ChromeOnly")


def prefIdentifier(pref):
    return pref.replace(".", "_").replace("-", "_")


def prefHeader(pref):
    return "mozilla/StaticPrefs_%s.h" % pref.partition(".")[0]


def computeGlobalNamesFromExposureSet(exposureSet):
    assert exposureSet is None or isinstance(exposureSet, set)

    if exposureSet:
        # Nonempty set
        return " | ".join(map(lambda g: "GlobalNames::%s" % g, sorted(exposureSet)))

    return "0"


class MemberCondition:
    """
    An object representing the condition for a member to actually be
    exposed.  Any of the arguments can be None.  If not
    None, they should have the following types:

    pref: The name of the preference.
    func: The name of the function.
    secureContext: A bool indicating whether a secure context is required.
    nonExposedGlobals: A set of names of globals.  Can be empty, in which case
                       it's treated the same way as None.
    trial: The name of the origin trial.
    """

    def __init__(
        self,
        pref=None,
        func=None,
        secureContext=False,
        nonExposedGlobals=None,
        trial=None,
    ):
        assert pref is None or isinstance(pref, str)
        assert func is None or isinstance(func, str)
        assert trial is None or isinstance(trial, str)
        assert isinstance(secureContext, bool)
        self.pref = pref
        if self.pref:
            identifier = prefIdentifier(self.pref)
            self.prefFuncIndex = "WebIDLPrefIndex::" + identifier
        else:
            self.prefFuncIndex = "WebIDLPrefIndex::NoPref"

        self.secureContext = secureContext

        def toFuncPtr(val):
            if val is None:
                return "nullptr"
            return "&" + val

        self.func = toFuncPtr(func)

        self.nonExposedGlobals = computeGlobalNamesFromExposureSet(nonExposedGlobals)

        if trial:
            self.trial = "OriginTrial::" + trial
        else:
            self.trial = "OriginTrial(0)"

    def __eq__(self, other):
        return (
            self.pref == other.pref
            and self.func == other.func
            and self.secureContext == other.secureContext
            and self.nonExposedGlobals == other.nonExposedGlobals
            and self.trial == other.trial
        )

    def __ne__(self, other):
        return not self.__eq__(other)

    def hasDisablers(self):
        return (
            self.pref is not None
            or self.secureContext
            or self.func != "nullptr"
            or self.nonExposedGlobals != "0"
            or self.trial != "OriginTrial(0)"
        )


class PropertyDefiner:
    """
    A common superclass for defining things on prototype objects.

    Subclasses should implement generateArray to generate the actual arrays of
    things we're defining.  They should also set self.chrome to the list of
    things only exposed to chrome and self.regular to the list of things exposed
    to both chrome and web pages.
    """

    def __init__(self, descriptor, name):
        self.descriptor = descriptor
        self.name = name

    def hasChromeOnly(self):
        return len(self.chrome) > 0

    def hasNonChromeOnly(self):
        return len(self.regular) > 0

    def variableName(self, chrome):
        if chrome:
            if self.hasChromeOnly():
                return "sChrome" + self.name
        else:
            if self.hasNonChromeOnly():
                return "s" + self.name
        return "nullptr"

    def usedForXrays(self):
        return self.descriptor.wantsXrays

    def length(self, chrome):
        return len(self.chrome) if chrome else len(self.regular)

    def __str__(self):
        # We only need to generate id arrays for things that will end
        # up used via ResolveProperty or EnumerateProperties.
        str = self.generateArray(self.regular, self.variableName(False))
        if self.hasChromeOnly():
            str += self.generateArray(self.chrome, self.variableName(True))
        return str

    @staticmethod
    def getStringAttr(member, name):
        attr = member.getExtendedAttribute(name)
        if attr is None:
            return None
        # It's a list of strings
        assert len(attr) == 1
        assert attr[0] is not None
        return attr[0]

    @staticmethod
    def getControllingCondition(interfaceMember, descriptor):
        interface = descriptor.interface
        nonExposureSet = interface.exposureSet - interfaceMember.exposureSet

        trial = PropertyDefiner.getStringAttr(interfaceMember, "Trial")
        if trial and interface.identifier.name in ["Window", "Document"]:
            raise TypeError(
                "[Trial] not yet supported for %s.%s, see bug 1757935"
                % (interface.identifier.name, interfaceMember.identifier.name)
            )

        return MemberCondition(
            PropertyDefiner.getStringAttr(interfaceMember, "Pref"),
            PropertyDefiner.getStringAttr(interfaceMember, "Func"),
            interfaceMember.getExtendedAttribute("SecureContext") is not None,
            nonExposureSet,
            trial,
        )

    @staticmethod
    def generatePrefableArrayValues(
        array,
        descriptor,
        specFormatter,
        specTerminator,
        getCondition,
        getDataTuple,
        switchToCondition=None,
    ):
        """
        This method generates an array of spec entries for interface members. It returns
          a tuple containing the array of spec entries and the maximum of the number of
          spec entries per condition.

        array is an array of interface members.

        descriptor is the descriptor for the interface that array contains members of.

        specFormatter is a function that takes a single argument, a tuple,
          and returns a string, a spec array entry.

        specTerminator is a terminator for the spec array (inserted every time
          our controlling pref changes and at the end of the array).

        getCondition is a callback function that takes an array entry and
          returns the corresponding MemberCondition.

        getDataTuple is a callback function that takes an array entry and
          returns a tuple suitable to be passed to specFormatter.

        switchToCondition is a function that takes a MemberCondition and an array of
          previously generated spec entries. If None is passed for this function then all
          the interface members should return the same value from getCondition.
        """

        def unsupportedSwitchToCondition(condition, specs):
            # If no specs have been added yet then this is just the first call to
            # switchToCondition that we call to avoid putting a specTerminator at the
            # front of the list.
            if len(specs) == 0:
                return
            raise "Not supported"

        if switchToCondition is None:
            switchToCondition = unsupportedSwitchToCondition

        specs = []
        numSpecsInCurPrefable = 0
        maxNumSpecsInPrefable = 0

        # So we won't put a specTerminator at the very front of the list:
        lastCondition = getCondition(array[0], descriptor)

        switchToCondition(lastCondition, specs)

        for member in array:
            curCondition = getCondition(member, descriptor)
            if lastCondition != curCondition:
                # Terminate previous list
                specs.append(specTerminator)
                if numSpecsInCurPrefable > maxNumSpecsInPrefable:
                    maxNumSpecsInPrefable = numSpecsInCurPrefable
                numSpecsInCurPrefable = 0
                # And switch to our new condition
                switchToCondition(curCondition, specs)
                lastCondition = curCondition
            # And the actual spec
            specs.append(specFormatter(getDataTuple(member, descriptor)))
            numSpecsInCurPrefable += 1
        if numSpecsInCurPrefable > maxNumSpecsInPrefable:
            maxNumSpecsInPrefable = numSpecsInCurPrefable
        specs.append(specTerminator)

        return (specs, maxNumSpecsInPrefable)

    def generatePrefableArray(
        self,
        array,
        name,
        specFormatter,
        specTerminator,
        specType,
        getCondition,
        getDataTuple,
    ):
        """
        This method generates our various arrays.

        array is an array of interface members as passed to generateArray

        name is the name as passed to generateArray

        specFormatter is a function that takes a single argument, a tuple,
          and returns a string, a spec array entry

        specTerminator is a terminator for the spec array (inserted every time
          our controlling pref changes and at the end of the array)

        specType is the actual typename of our spec

        getCondition is a callback function that takes an array entry and
          returns the corresponding MemberCondition.

        getDataTuple is a callback function that takes an array entry and
          returns a tuple suitable to be passed to specFormatter.
        """

        # We want to generate a single list of specs, but with specTerminator
        # inserted at every point where the pref name controlling the member
        # changes.  That will make sure the order of the properties as exposed
        # on the interface and interface prototype objects does not change when
        # pref control is added to members while still allowing us to define all
        # the members in the smallest number of JSAPI calls.
        assert len(array) != 0

        disablers = []
        prefableSpecs = []

        disablersTemplate = dedent(
            """
            static const PrefableDisablers %s_disablers%d = {
              %s, %s, %s, %s, %s
            };
            """
        )
        prefableWithDisablersTemplate = "  { &%s_disablers%d, &%s_specs[%d] }"
        prefableWithoutDisablersTemplate = "  { nullptr, &%s_specs[%d] }"

        def switchToCondition(condition, specs):
            # Set up pointers to the new sets of specs inside prefableSpecs
            if condition.hasDisablers():
                prefableSpecs.append(
                    prefableWithDisablersTemplate % (name, len(specs), name, len(specs))
                )
                disablers.append(
                    disablersTemplate
                    % (
                        name,
                        len(specs),
                        condition.prefFuncIndex,
                        condition.nonExposedGlobals,
                        toStringBool(condition.secureContext),
                        condition.trial,
                        condition.func,
                    )
                )
            else:
                prefableSpecs.append(
                    prefableWithoutDisablersTemplate % (name, len(specs))
                )

        specs, maxNumSpecsInPrefable = self.generatePrefableArrayValues(
            array,
            self.descriptor,
            specFormatter,
            specTerminator,
            getCondition,
            getDataTuple,
            switchToCondition,
        )
        prefableSpecs.append("  { nullptr, nullptr }")

        specType = "const " + specType
        arrays = fill(
            """
            MOZ_GLOBINIT static ${specType} ${name}_specs[] = {
            ${specs}
            };

            ${disablers}
            static const Prefable<${specType}> ${name}[] = {
            ${prefableSpecs}
            };

            """,
            specType=specType,
            name=name,
            disablers="\n".join(disablers),
            specs=",\n".join(specs),
            prefableSpecs=",\n".join(prefableSpecs),
        )

        if self.usedForXrays():
            arrays = fill(
                """
                $*{arrays}
                static_assert(${numPrefableSpecs} <= 1ull << NUM_BITS_PROPERTY_INFO_PREF_INDEX,
                    "We have a prefable index that is >= (1 << NUM_BITS_PROPERTY_INFO_PREF_INDEX)");
                static_assert(${maxNumSpecsInPrefable} <= 1ull << NUM_BITS_PROPERTY_INFO_SPEC_INDEX,
                    "We have a spec index that is >= (1 << NUM_BITS_PROPERTY_INFO_SPEC_INDEX)");

                """,
                arrays=arrays,
                # Minus 1 because there's a list terminator in prefableSpecs.
                numPrefableSpecs=len(prefableSpecs) - 1,
                maxNumSpecsInPrefable=maxNumSpecsInPrefable,
            )

        return arrays


# The length of a method is the minimum of the lengths of the
# argument lists of all its overloads.
def overloadLength(arguments):
    i = len(arguments)
    while i > 0 and arguments[i - 1].optional:
        i -= 1
    return i


def methodLength(method):
    signatures = method.signatures()
    return min(overloadLength(arguments) for retType, arguments in signatures)


def clearableCachedAttrs(descriptor):
    return (
        m
        for m in descriptor.interface.members
        if m.isAttr() and
        # Constants should never need clearing!
        m.dependsOn != "Nothing" and m.slotIndices is not None
    )


def MakeClearCachedValueNativeName(member):
    return "ClearCached%sValue" % MakeNativeName(member.identifier.name)


def IDLToCIdentifier(name):
    return name.replace("-", "_")


def EnumerabilityFlags(member):
    if member.getExtendedAttribute("NonEnumerable"):
        return "0"
    return "JSPROP_ENUMERATE"


class MethodDefiner(PropertyDefiner):
    """
    A class for defining methods on a prototype object.
    """

    def __init__(self, descriptor, name, crossOriginOnly, static, unforgeable=False):
        assert not (static and unforgeable)
        PropertyDefiner.__init__(self, descriptor, name)

        # FIXME https://bugzilla.mozilla.org/show_bug.cgi?id=772822
        #       We should be able to check for special operations without an
        #       identifier. For now we check if the name starts with __

        # Ignore non-static methods for interfaces without a proto object
        if descriptor.interface.hasInterfacePrototypeObject() or static:
            methods = [
                m
                for m in descriptor.interface.members
                if m.isMethod()
                and m.isStatic() == static
                and MemberIsLegacyUnforgeable(m, descriptor) == unforgeable
                and (
                    not crossOriginOnly or m.getExtendedAttribute("CrossOriginCallable")
                )
                and not m.isIdentifierLess()
                and not m.getExtendedAttribute("Unexposed")
            ]
        else:
            methods = []
        self.chrome = []
        self.regular = []
        for m in methods:
            method = self.methodData(m, descriptor)

            if m.isStatic():
                method["nativeName"] = CppKeywords.checkMethodName(
                    IDLToCIdentifier(m.identifier.name)
                )

            if isChromeOnly(m):
                self.chrome.append(method)
            else:
                self.regular.append(method)

        # TODO: Once iterable is implemented, use tiebreak rules instead of
        # failing. Also, may be more tiebreak rules to implement once spec bug
        # is resolved.
        # https://www.w3.org/Bugs/Public/show_bug.cgi?id=28592
        def hasIterator(methods, regular):
            return any("@@iterator" in m.aliases for m in methods) or any(
                "@@iterator" == r["name"] for r in regular
            )

        # Check whether we need to output an @@iterator due to having an indexed
        # getter.  We only do this while outputting non-static and
        # non-unforgeable methods, since the @@iterator function will be
        # neither.
        if not static and not unforgeable and descriptor.supportsIndexedProperties():
            if hasIterator(methods, self.regular):
                raise TypeError(
                    "Cannot have indexed getter/attr on "
                    "interface %s with other members "
                    "that generate @@iterator, such as "
                    "maplike/setlike or aliased functions."
                    % self.descriptor.interface.identifier.name
                )
            self.regular.append(
                {
                    "name": "@@iterator",
                    "methodInfo": False,
                    "selfHostedName": "$ArrayValues",
                    "length": 0,
                    "flags": "0",  # Not enumerable, per spec.
                    "condition": MemberCondition(),
                }
            )

        # Generate the keys/values/entries aliases for value iterables.
        maplikeOrSetlikeOrIterable = descriptor.interface.maplikeOrSetlikeOrIterable
        if (
            not static
            and not unforgeable
            and maplikeOrSetlikeOrIterable
            and maplikeOrSetlikeOrIterable.isIterable()
            and maplikeOrSetlikeOrIterable.isValueIterator()
        ):
            # Add our keys/values/entries/forEach
            self.regular.append(
                {
                    "name": "keys",
                    "methodInfo": False,
                    "selfHostedName": "ArrayKeys",
                    "length": 0,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        maplikeOrSetlikeOrIterable, descriptor
                    ),
                }
            )
            self.regular.append(
                {
                    "name": "values",
                    "methodInfo": False,
                    "selfHostedName": "$ArrayValues",
                    "length": 0,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        maplikeOrSetlikeOrIterable, descriptor
                    ),
                }
            )
            self.regular.append(
                {
                    "name": "entries",
                    "methodInfo": False,
                    "selfHostedName": "ArrayEntries",
                    "length": 0,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        maplikeOrSetlikeOrIterable, descriptor
                    ),
                }
            )
            self.regular.append(
                {
                    "name": "forEach",
                    "methodInfo": False,
                    "selfHostedName": "ArrayForEach",
                    "length": 1,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        maplikeOrSetlikeOrIterable, descriptor
                    ),
                }
            )

        if not static:
            stringifier = descriptor.operations["Stringifier"]
            if stringifier and unforgeable == MemberIsLegacyUnforgeable(
                stringifier, descriptor
            ):
                toStringDesc = {
                    "name": GetWebExposedName(stringifier, descriptor),
                    "nativeName": stringifier.identifier.name,
                    "length": 0,
                    "flags": "JSPROP_ENUMERATE",
                    "condition": PropertyDefiner.getControllingCondition(
                        stringifier, descriptor
                    ),
                }
                if isChromeOnly(stringifier):
                    self.chrome.append(toStringDesc)
                else:
                    self.regular.append(toStringDesc)
            if unforgeable and descriptor.interface.getExtendedAttribute(
                "LegacyUnforgeable"
            ):
                # Synthesize our valueOf method
                self.regular.append(
                    {
                        "name": "valueOf",
                        "selfHostedName": "Object_valueOf",
                        "methodInfo": False,
                        "length": 0,
                        "flags": "0",  # readonly/permanent added automatically.
                        "condition": MemberCondition(),
                    }
                )

        if descriptor.interface.isJSImplemented():
            if static:
                if descriptor.interface.hasInterfaceObject():
                    self.chrome.append(
                        {
                            "name": "_create",
                            "nativeName": ("%s::_Create" % descriptor.name),
                            "methodInfo": False,
                            "length": 2,
                            "flags": "0",
                            "condition": MemberCondition(),
                        }
                    )

        self.unforgeable = unforgeable

        if static:
            if not descriptor.interface.hasInterfaceObject():
                # static methods go on the interface object
                assert not self.hasChromeOnly() and not self.hasNonChromeOnly()
        else:
            if not descriptor.interface.hasInterfacePrototypeObject():
                # non-static methods go on the interface prototype object
                assert not self.hasChromeOnly() and not self.hasNonChromeOnly()

    @staticmethod
    def methodData(m, descriptor, overrideFlags=None):
        return {
            "name": m.identifier.name,
            "methodInfo": not m.isStatic(),
            "length": methodLength(m),
            "flags": (
                EnumerabilityFlags(m) if (overrideFlags is None) else overrideFlags
            ),
            "condition": PropertyDefiner.getControllingCondition(m, descriptor),
            "allowCrossOriginThis": m.getExtendedAttribute("CrossOriginCallable"),
            "returnsPromise": m.returnsPromise(),
            "hasIteratorAlias": "@@iterator" in m.aliases,
        }

    @staticmethod
    def formatSpec(fields):
        if fields[0].startswith("@@"):
            fields = (fields[0][2:],) + fields[1:]
            return "  JS_SYM_FNSPEC(%s, %s, %s, %s, %s, %s)" % fields
        return '  JS_FNSPEC("%s", %s, %s, %s, %s, %s)' % fields

    @staticmethod
    def specData(m, descriptor, unforgeable=False):
        def flags(m, unforgeable):
            unforgeable = " | JSPROP_PERMANENT | JSPROP_READONLY" if unforgeable else ""
            return m["flags"] + unforgeable

        if "selfHostedName" in m:
            selfHostedName = '"%s"' % m["selfHostedName"]
            assert not m.get("methodInfo", True)
            accessor = "nullptr"
            jitinfo = "nullptr"
        else:
            selfHostedName = "nullptr"
            # When defining symbols, function name may not match symbol name
            methodName = m.get("methodName", m["name"])
            accessor = m.get("nativeName", IDLToCIdentifier(methodName))
            if m.get("methodInfo", True):
                if m.get("returnsPromise", False):
                    exceptionPolicy = "ConvertExceptionsToPromises"
                else:
                    exceptionPolicy = "ThrowExceptions"

                # Cast this in case the methodInfo is a
                # JSTypedMethodJitInfo.
                jitinfo = (
                    "reinterpret_cast<const JSJitInfo*>(&%s_methodinfo)" % accessor
                )
                if m.get("allowCrossOriginThis", False):
                    accessor = (
                        "(GenericMethod<CrossOriginThisPolicy, %s>)" % exceptionPolicy
                    )
                elif descriptor.interface.hasDescendantWithCrossOriginMembers:
                    accessor = (
                        "(GenericMethod<MaybeCrossOriginObjectThisPolicy, %s>)"
                        % exceptionPolicy
                    )
                elif descriptor.interface.isOnGlobalProtoChain():
                    accessor = (
                        "(GenericMethod<MaybeGlobalThisPolicy, %s>)" % exceptionPolicy
                    )
                else:
                    accessor = "(GenericMethod<NormalThisPolicy, %s>)" % exceptionPolicy
            else:
                if m.get("returnsPromise", False):
                    jitinfo = "&%s_methodinfo" % accessor
                    accessor = "StaticMethodPromiseWrapper"
                else:
                    jitinfo = "nullptr"

        return (
            m["name"],
            accessor,
            jitinfo,
            m["length"],
            flags(m, unforgeable),
            selfHostedName,
        )

    @staticmethod
    def condition(m, d):
        return m["condition"]

    def generateArray(self, array, name):
        if len(array) == 0:
            return ""

        return self.generatePrefableArray(
            array,
            name,
            self.formatSpec,
            "  JS_FS_END",
            "JSFunctionSpec",
            self.condition,
            functools.partial(self.specData, unforgeable=self.unforgeable),
        )


class AttrDefiner(PropertyDefiner):
    def __init__(self, descriptor, name, crossOriginOnly, static, unforgeable=False):
        assert not (static and unforgeable)
        PropertyDefiner.__init__(self, descriptor, name)
        self.name = name
        # Ignore non-static attributes for interfaces without a proto object
        if descriptor.interface.hasInterfacePrototypeObject() or static:
            idlAttrs = [
                m
                for m in descriptor.interface.members
                if m.isAttr()
                and m.isStatic() == static
                and MemberIsLegacyUnforgeable(m, descriptor) == unforgeable
                and (
                    not crossOriginOnly
                    or m.getExtendedAttribute("CrossOriginReadable")
                    or m.getExtendedAttribute("CrossOriginWritable")
                )
            ]
        else:
            idlAttrs = []

        attributes = []
        for attr in idlAttrs:
            attributes.extend(self.attrData(attr, unforgeable))
        self.chrome = [m for m in attributes if isChromeOnly(m["attr"])]
        self.regular = [m for m in attributes if not isChromeOnly(m["attr"])]
        self.static = static

        if static:
            if not descriptor.interface.hasInterfaceObject():
                # static attributes go on the interface object
                assert not self.hasChromeOnly() and not self.hasNonChromeOnly()
        else:
            if not descriptor.interface.hasInterfacePrototypeObject():
                # non-static attributes go on the interface prototype object
                assert not self.hasChromeOnly() and not self.hasNonChromeOnly()

    @staticmethod
    def attrData(attr, unforgeable=False, overrideFlags=None):
        if overrideFlags is None:
            permanent = " | JSPROP_PERMANENT" if unforgeable else ""
            flags = EnumerabilityFlags(attr) + permanent
        else:
            flags = overrideFlags
        return (
            {"name": name, "attr": attr, "flags": flags}
            for name in [attr.identifier.name] + attr.bindingAliases
        )

    @staticmethod
    def condition(m, d):
        return PropertyDefiner.getControllingCondition(m["attr"], d)

    @staticmethod
    def specData(entry, descriptor, static=False, crossOriginOnly=False):
        def getter(attr):
            if crossOriginOnly and not attr.getExtendedAttribute("CrossOriginReadable"):
                return "nullptr, nullptr"
            if static:
                if attr.type.isPromise():
                    raise TypeError(
                        "Don't know how to handle "
                        "static Promise-returning "
                        "attribute %s.%s" % (descriptor.name, attr.identifier.name)
                    )
                accessor = "get_" + IDLToCIdentifier(attr.identifier.name)
                jitinfo = "nullptr"
            else:
                if attr.type.isPromise():
                    exceptionPolicy = "ConvertExceptionsToPromises"
                else:
                    exceptionPolicy = "ThrowExceptions"

                if attr.hasLegacyLenientThis():
                    if attr.getExtendedAttribute("CrossOriginReadable"):
                        raise TypeError(
                            "Can't handle lenient cross-origin "
                            "readable attribute %s.%s"
                            % (descriptor.name, attr.identifier.name)
                        )
                    if descriptor.interface.hasDescendantWithCrossOriginMembers:
                        accessor = (
                            "GenericGetter<MaybeCrossOriginObjectLenientThisPolicy, %s>"
                            % exceptionPolicy
                        )
                    else:
                        accessor = (
                            "GenericGetter<LenientThisPolicy, %s>" % exceptionPolicy
                        )
                elif attr.getExtendedAttribute("CrossOriginReadable"):
                    accessor = (
                        "GenericGetter<CrossOriginThisPolicy, %s>" % exceptionPolicy
                    )
                elif descriptor.interface.hasDescendantWithCrossOriginMembers:
                    accessor = (
                        "GenericGetter<MaybeCrossOriginObjectThisPolicy, %s>"
                        % exceptionPolicy
                    )
                elif descriptor.interface.isOnGlobalProtoChain():
                    accessor = (
                        "GenericGetter<MaybeGlobalThisPolicy, %s>" % exceptionPolicy
                    )
                else:
                    accessor = "GenericGetter<NormalThisPolicy, %s>" % exceptionPolicy
                jitinfo = "&%s_getterinfo" % IDLToCIdentifier(attr.identifier.name)
            return "%s, %s" % (accessor, jitinfo)

        def setter(attr):
            if (
                attr.readonly
                and attr.getExtendedAttribute("PutForwards") is None
                and attr.getExtendedAttribute("Replaceable") is None
                and attr.getExtendedAttribute("LegacyLenientSetter") is None
            ):
                return "nullptr, nullptr"
            if crossOriginOnly and not attr.getExtendedAttribute("CrossOriginWritable"):
                return "nullptr, nullptr"
            if static:
                accessor = "set_" + IDLToCIdentifier(attr.identifier.name)
                jitinfo = "nullptr"
            else:
                if attr.hasLegacyLenientThis():
                    if attr.getExtendedAttribute("CrossOriginWritable"):
                        raise TypeError(
                            "Can't handle lenient cross-origin "
                            "writable attribute %s.%s"
                            % (descriptor.name, attr.identifier.name)
                        )
                    if descriptor.interface.hasDescendantWithCrossOriginMembers:
                        accessor = (
                            "GenericSetter<MaybeCrossOriginObjectLenientThisPolicy>"
                        )
                    else:
                        accessor = "GenericSetter<LenientThisPolicy>"
                elif attr.getExtendedAttribute("CrossOriginWritable"):
                    accessor = "GenericSetter<CrossOriginThisPolicy>"
                elif descriptor.interface.hasDescendantWithCrossOriginMembers:
                    accessor = "GenericSetter<MaybeCrossOriginObjectThisPolicy>"
                elif descriptor.interface.isOnGlobalProtoChain():
                    accessor = "GenericSetter<MaybeGlobalThisPolicy>"
                else:
                    accessor = "GenericSetter<NormalThisPolicy>"
                jitinfo = "&%s_setterinfo" % IDLToCIdentifier(attr.identifier.name)
            return "%s, %s" % (accessor, jitinfo)

        name, attr, flags = entry["name"], entry["attr"], entry["flags"]
        return (name, flags, getter(attr), setter(attr))

    @staticmethod
    def formatSpec(fields):
        return '  JSPropertySpec::nativeAccessors("%s", %s, %s, %s)' % fields

    def generateArray(self, array, name):
        if len(array) == 0:
            return ""

        return self.generatePrefableArray(
            array,
            name,
            self.formatSpec,
            "  JS_PS_END",
            "JSPropertySpec",
            self.condition,
            functools.partial(self.specData, static=self.static),
        )


class ConstDefiner(PropertyDefiner):
    """
    A class for definining constants on the interface object
    """

    def __init__(self, descriptor, name):
        PropertyDefiner.__init__(self, descriptor, name)
        self.name = name
        constants = [m for m in descriptor.interface.members if m.isConst()]
        self.chrome = [m for m in constants if isChromeOnly(m)]
        self.regular = [m for m in constants if not isChromeOnly(m)]

    def generateArray(self, array, name):
        if len(array) == 0:
            return ""

        def specData(const, descriptor):
            return (const.identifier.name, convertConstIDLValueToJSVal(const.value))

        return self.generatePrefableArray(
            array,
            name,
            lambda fields: '  { "%s", %s }' % fields,
            "  { 0, JS::UndefinedValue() }",
            "ConstantSpec",
            PropertyDefiner.getControllingCondition,
            specData,
        )


class PropertyArrays:
    def __init__(self, descriptor, crossOriginOnly=False):
        self.staticMethods = MethodDefiner(
            descriptor, "StaticMethods", crossOriginOnly, static=True
        )
        self.staticAttrs = AttrDefiner(
            descriptor, "StaticAttributes", crossOriginOnly, static=True
        )
        self.methods = MethodDefiner(
            descriptor, "Methods", crossOriginOnly, static=False
        )
        self.attrs = AttrDefiner(
            descriptor, "Attributes", crossOriginOnly, static=False
        )
        self.unforgeableMethods = MethodDefiner(
            descriptor,
            "UnforgeableMethods",
            crossOriginOnly,
            static=False,
            unforgeable=True,
        )
        self.unforgeableAttrs = AttrDefiner(
            descriptor,
            "UnforgeableAttributes",
            crossOriginOnly,
            static=False,
            unforgeable=True,
        )
        self.consts = ConstDefiner(descriptor, "Constants")

    @staticmethod
    def arrayNames():
        return [
            "staticMethods",
            "staticAttrs",
            "methods",
            "attrs",
            "unforgeableMethods",
            "unforgeableAttrs",
            "consts",
        ]

    def hasChromeOnly(self):
        return any(getattr(self, a).hasChromeOnly() for a in self.arrayNames())

    def hasNonChromeOnly(self):
        return any(getattr(self, a).hasNonChromeOnly() for a in self.arrayNames())

    def __str__(self):
        define = ""
        for array in self.arrayNames():
            define += str(getattr(self, array))
        return define


class CGConstDefinition(CGThing):
    """
    Given a const member of an interface, return the C++ static const definition
    for the member. Should be part of the interface namespace in the header
    file.
    """

    def __init__(self, member):
        assert (
            member.isConst()
            and member.value.type.isPrimitive()
            and not member.value.type.nullable()
        )

        name = CppKeywords.checkMethodName(IDLToCIdentifier(member.identifier.name))
        tag = member.value.type.tag()
        value = member.value.value
        if tag == IDLType.Tags.bool:
            value = toStringBool(member.value.value)
        self.const = "static const %s %s = %s;" % (builtinNames[tag], name, value)

    def declare(self):
        return self.const

    def define(self):
        return ""

    def deps(self):
        return []


class CGNativeProperties(CGList):
    def __init__(self, descriptor, properties):
        def generateNativeProperties(name, chrome):
            def check(p):
                return p.hasChromeOnly() if chrome else p.hasNonChromeOnly()

            nativePropsInts = []
            nativePropsPtrs = []
            nativePropsDuos = []

            duosOffset = 0
            idsOffset = 0
            for array in properties.arrayNames():
                propertyArray = getattr(properties, array)
                if check(propertyArray):
                    varName = propertyArray.variableName(chrome)
                    bitfields = "true,  %d /* %s */" % (duosOffset, varName)
                    duosOffset += 1
                    nativePropsInts.append(CGGeneric(bitfields))

                    if propertyArray.usedForXrays():
                        ids = "&%s_propertyInfos[%d]" % (name, idsOffset)
                        idsOffset += propertyArray.length(chrome)
                    else:
                        ids = "nullptr"
                    duo = "{ %s, %s }" % (varName, ids)
                    nativePropsDuos.append(CGGeneric(duo))
                else:
                    bitfields = "false, 0"
                    nativePropsInts.append(CGGeneric(bitfields))

            iteratorAliasIndex = -1
            for index, item in enumerate(properties.methods.regular):
                if item.get("hasIteratorAlias"):
                    iteratorAliasIndex = index
                    break
            nativePropsInts.append(CGGeneric(str(iteratorAliasIndex)))

            nativePropsDuos = [
                CGWrapper(
                    CGIndenter(CGList(nativePropsDuos, ",\n")), pre="{\n", post="\n}"
                )
            ]

            pre = "static const NativePropertiesN<%d> %s = {\n" % (duosOffset, name)
            post = "\n};\n"
            if descriptor.wantsXrays:
                pre = fill(
                    """
                    static uint16_t ${name}_sortedPropertyIndices[${size}];
                    static PropertyInfo ${name}_propertyInfos[${size}];

                    $*{pre}
                    """,
                    name=name,
                    size=idsOffset,
                    pre=pre,
                )
                if iteratorAliasIndex > 0:
                    # The iteratorAliasMethodIndex is a signed integer, so the
                    # max value it can store is 2^(nbits-1)-1.
                    post = fill(
                        """
                        $*{post}
                        static_assert(${iteratorAliasIndex} < 1ull << (CHAR_BIT * sizeof(${name}.iteratorAliasMethodIndex) - 1),
                            "We have an iterator alias index that is oversized");
                        """,
                        post=post,
                        iteratorAliasIndex=iteratorAliasIndex,
                        name=name,
                    )
                post = fill(
                    """
                    $*{post}
                    static_assert(${propertyInfoCount} < 1ull << (CHAR_BIT * sizeof(${name}.propertyInfoCount)),
                        "We have a property info count that is oversized");
                    """,
                    post=post,
                    propertyInfoCount=idsOffset,
                    name=name,
                )
                nativePropsInts.append(CGGeneric("%d" % idsOffset))
                nativePropsPtrs.append(CGGeneric("%s_sortedPropertyIndices" % name))
            else:
                nativePropsInts.append(CGGeneric("0"))
                nativePropsPtrs.append(CGGeneric("nullptr"))
            nativeProps = nativePropsInts + nativePropsPtrs + nativePropsDuos
            return CGWrapper(CGIndenter(CGList(nativeProps, ",\n")), pre=pre, post=post)

        nativeProperties = []
        if properties.hasNonChromeOnly():
            nativeProperties.append(
                generateNativeProperties("sNativeProperties", False)
            )
        if properties.hasChromeOnly():
            nativeProperties.append(
                generateNativeProperties("sChromeOnlyNativeProperties", True)
            )

        CGList.__init__(self, nativeProperties, "\n")

    def declare(self):
        return ""

    def define(self):
        return CGList.define(self)


class CGCollectJSONAttributesMethod(CGAbstractMethod):
    """
    Generate the CollectJSONAttributes method for an interface descriptor
    """

    def __init__(self, descriptor, toJSONMethod):
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("%s*" % descriptor.nativeType, "self"),
            Argument("JS::Rooted<JSObject*>&", "result"),
        ]
        CGAbstractMethod.__init__(
            self, descriptor, "CollectJSONAttributes", "bool", args, canRunScript=True
        )
        self.toJSONMethod = toJSONMethod

    def definition_body(self):
        ret = ""
        interface = self.descriptor.interface
        toJSONCondition = PropertyDefiner.getControllingCondition(
            self.toJSONMethod, self.descriptor
        )
        needUnwrappedObj = False
        for m in interface.members:
            if m.isAttr() and not m.isStatic() and m.type.isJSONType():
                getAndDefine = fill(
                    """
                    JS::Rooted<JS::Value> temp(cx);
                    if (!get_${name}(cx, obj, self, JSJitGetterCallArgs(&temp))) {
                      return false;
                    }
                    if (!JS_DefineProperty(cx, result, "${name}", temp, JSPROP_ENUMERATE)) {
                      return false;
                    }
                    """,
                    name=IDLToCIdentifier(m.identifier.name),
                )
                # Make sure we don't include things which are supposed to be
                # disabled.  Things that either don't have disablers or whose
                # disablers match the disablers for our toJSON method can't
                # possibly be disabled, but other things might be.
                condition = PropertyDefiner.getControllingCondition(m, self.descriptor)
                if condition.hasDisablers() and condition != toJSONCondition:
                    needUnwrappedObj = True
                    ret += fill(
                        """
                        // This is unfortunately a linear scan through sAttributes, but we
                        // only do it for things which _might_ be disabled, which should
                        // help keep the performance problems down.
                        if (IsGetterEnabled(cx, unwrappedObj, (JSJitGetterOp)get_${name}, sAttributes)) {
                          $*{getAndDefine}
                        }
                        """,
                        name=IDLToCIdentifier(m.identifier.name),
                        getAndDefine=getAndDefine,
                    )
                else:
                    ret += fill(
                        """
                        { // scope for "temp"
                          $*{getAndDefine}
                        }
                        """,
                        getAndDefine=getAndDefine,
                    )
        ret += "return true;\n"

        if needUnwrappedObj:
            # If we started allowing cross-origin objects here, we'd need to
            # use CheckedUnwrapDynamic and figure out whether it makes sense.
            # But in practice no one is trying to add toJSON methods to those,
            # so let's just guard against it.
            assert not self.descriptor.isMaybeCrossOriginObject()
            ret = fill(
                """
                JS::Rooted<JSObject*> unwrappedObj(cx, js::CheckedUnwrapStatic(obj));
                if (!unwrappedObj) {
                  // How did that happen?  We managed to get called with that
                  // object as "this"!  Just give up on sanity.
                  return false;
                }

                $*{ret}
                """,
                ret=ret,
            )

        return ret


class CGCreateInterfaceObjectsMethod(CGAbstractMethod):
    """
    Generate the CreateInterfaceObjects method for an interface descriptor.

    properties should be a PropertyArrays instance.
    """

    def __init__(
        self, descriptor, properties, haveUnscopables, haveLegacyWindowAliases, static
    ):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("JS::Handle<JSObject*>", "aGlobal"),
            Argument("ProtoAndIfaceCache&", "aProtoAndIfaceCache"),
            Argument("DefineInterfaceProperty", "aDefineOnGlobal"),
        ]
        CGAbstractMethod.__init__(
            self, descriptor, "CreateInterfaceObjects", "void", args, static=static
        )
        self.properties = properties
        self.haveUnscopables = haveUnscopables
        self.haveLegacyWindowAliases = haveLegacyWindowAliases

    def definition_body(self):
        needInterfaceObject = self.descriptor.interface.hasInterfaceObject()
        if needInterfaceObject and self.descriptor.isExposedConditionally():
            # This code might be called when we're trying to create an object
            # in a non-system compartment, for example when system code is
            # calling a constructor through Xrays. In that case we do want to
            # create an interface object in the non-system compartment, but we
            # don't want to expose the name on the non-system global if the
            # interface itself is marked as ChromeOnly.
            defineOnGlobal = (
                "ShouldExpose<%s::ConstructorEnabled>(aCx, aGlobal, aDefineOnGlobal)"
                % toBindingNamespace(self.descriptor.name)
            )
        else:
            defineOnGlobal = "aDefineOnGlobal != DefineInterfaceProperty::No"
        if needInterfaceObject:
            if self.descriptor.interface.isNamespace():
                if self.descriptor.interface.getExtendedAttribute("ProtoObjectHack"):
                    getConstructorProto = "GetHackedNamespaceProtoObject"
                else:
                    getConstructorProto = "JS::GetRealmObjectPrototype"
                getConstructorProto = "aCx, " + getConstructorProto
                constructorProtoType = "Rooted"
            else:
                getConstructorProto = InterfaceObjectProtoGetter(self.descriptor)
                constructorProtoType = "Handle"

            getConstructorProto = fill(
                """
                JS::${type}<JSObject*> constructorProto(${getConstructorProto}(aCx));
                if (!constructorProto) {
                  return;
                }
                """,
                type=constructorProtoType,
                getConstructorProto=getConstructorProto,
            )

            interfaceInfo = "&sInterfaceObjectInfo"
            interfaceCache = (
                "&aProtoAndIfaceCache.EntrySlotOrCreate(constructors::id::%s)"
                % self.descriptor.name
            )
            getConstructorProto = CGGeneric(getConstructorProto)
            constructorProto = "constructorProto"
        else:
            # We don't have slots to store the legacy factory functions.
            assert len(self.descriptor.interface.legacyFactoryFunctions) == 0
            interfaceInfo = "nullptr"
            interfaceCache = "nullptr"
            getConstructorProto = None
            constructorProto = "nullptr"

        if self.properties.hasNonChromeOnly():
            properties = "sNativeProperties.Upcast()"
        else:
            properties = "nullptr"
        if self.properties.hasChromeOnly():
            chromeProperties = "sChromeOnlyNativeProperties.Upcast()"
        else:
            chromeProperties = "nullptr"

        # We use getClassName here. This should be the right thing to pass as
        # the name argument to CreateInterfaceObjects. This is generally the
        # interface identifier, except for the synthetic interfaces created for
        # the default iterator objects. If needInterfaceObject is true then
        # we'll use the name to install a property on the global object, so
        # there shouldn't be any spaces in the name.
        name = self.descriptor.interface.getClassName()
        assert not (needInterfaceObject and " " in name)

        if self.descriptor.interface.isNamespace():
            # If we don't need to create anything, why are we generating this?
            assert needInterfaceObject

            call = fill(
                """
                JS::Heap<JSObject*>* interfaceCache = ${interfaceCache};
                dom::CreateNamespaceObject(aCx, aGlobal, ${constructorProto},
                                           sNamespaceObjectClass,
                                           interfaceCache,
                                           ${properties},
                                           ${chromeProperties},
                                           "${name}",
                                           ${defineOnGlobal});
                """,
                interfaceCache=interfaceCache,
                constructorProto=constructorProto,
                properties=properties,
                chromeProperties=chromeProperties,
                name=name,
                defineOnGlobal=defineOnGlobal,
            )
            return CGList(
                [
                    getConstructorProto,
                    CGGeneric(call),
                ],
                "\n",
            ).define()

        needInterfacePrototypeObject = (
            self.descriptor.interface.hasInterfacePrototypeObject()
        )

        # If we don't need to create anything, why are we generating this?
        assert needInterfaceObject or needInterfacePrototypeObject

        if needInterfacePrototypeObject:
            (protoGetter, protoHandleGetter) = InterfacePrototypeObjectProtoGetter(
                self.descriptor
            )
            if protoHandleGetter is None:
                parentProtoType = "Rooted"
                getParentProto = "aCx, " + protoGetter
            else:
                parentProtoType = "Handle"
                getParentProto = protoHandleGetter

            getParentProto = fill(
                """
                JS::${type}<JSObject*> parentProto(${getParentProto}(aCx));
                if (!parentProto) {
                  return;
                }
                """,
                type=parentProtoType,
                getParentProto=getParentProto,
            )

            protoClass = "&sPrototypeClass"
            protoCache = (
                "&aProtoAndIfaceCache.EntrySlotOrCreate(prototypes::id::%s)"
                % self.descriptor.name
            )
            parentProto = "parentProto"
            getParentProto = CGGeneric(getParentProto)
        else:
            protoClass = "nullptr"
            protoCache = "nullptr"
            parentProto = "nullptr"
            getParentProto = None

        if self.descriptor.interface.ctor():
            constructArgs = methodLength(self.descriptor.interface.ctor())
            isConstructorChromeOnly = isChromeOnly(self.descriptor.interface.ctor())
        else:
            constructArgs = 0
            isConstructorChromeOnly = False
        if len(self.descriptor.interface.legacyFactoryFunctions) > 0:
            legacyFactoryFunctions = "Span(legacyFactoryFunctions)"
        else:
            legacyFactoryFunctions = "Span<const LegacyFactoryFunction, 0>{}"

        isGlobal = self.descriptor.isGlobal() is not None

        ensureCaches = fill(
            """
            JS::Heap<JSObject*>* protoCache = ${protoCache};
            JS::Heap<JSObject*>* interfaceCache = ${interfaceCache};
            """,
            protoCache=protoCache,
            interfaceCache=interfaceCache,
        )
        call = fill(
            """
            dom::CreateInterfaceObjects(aCx, aGlobal, ${parentProto},
                                        ${protoClass}, protoCache,
                                        ${constructorProto}, ${interfaceInfo}, ${constructArgs}, ${isConstructorChromeOnly}, ${legacyFactoryFunctions},
                                        interfaceCache,
                                        ${properties},
                                        ${chromeProperties},
                                        "${name}",
                                        ${defineOnGlobal},
                                        ${unscopableNames},
                                        ${isGlobal},
                                        ${legacyWindowAliases});
            """,
            protoClass=protoClass,
            parentProto=parentProto,
            constructorProto=constructorProto,
            interfaceInfo=interfaceInfo,
            constructArgs=constructArgs,
            isConstructorChromeOnly=toStringBool(isConstructorChromeOnly),
            legacyFactoryFunctions=legacyFactoryFunctions,
            properties=properties,
            chromeProperties=chromeProperties,
            name=name,
            defineOnGlobal=defineOnGlobal,
            unscopableNames="unscopableNames" if self.haveUnscopables else "nullptr",
            isGlobal=toStringBool(isGlobal),
            legacyWindowAliases=(
                "legacyWindowAliases" if self.haveLegacyWindowAliases else "nullptr"
            ),
        )

        # If we fail after here, we must clear interface and prototype caches
        # using this code: intermediate failure must not expose the interface in
        # partially-constructed state.  Note that every case after here needs an
        # interface prototype object.
        failureCode = dedent(
            """
            *protoCache = nullptr;
            if (interfaceCache) {
              *interfaceCache = nullptr;
            }
            return;
            """
        )

        needProtoVar = False

        aliasedMembers = [
            m for m in self.descriptor.interface.members if m.isMethod() and m.aliases
        ]
        if aliasedMembers:
            assert needInterfacePrototypeObject

            def defineAlias(alias):
                if alias == "@@iterator" or alias == "@@asyncIterator":
                    name = alias[2:]

                    symbolJSID = (
                        "JS::GetWellKnownSymbolKey(aCx, JS::SymbolCode::%s)" % name
                    )
                    prop = "%sId" % name
                    getSymbolJSID = CGGeneric(
                        fill(
                            "JS::Rooted<jsid> ${prop}(aCx, ${symbolJSID});",
                            prop=prop,
                            symbolJSID=symbolJSID,
                        )
                    )
                    defineFn = "JS_DefinePropertyById"
                    enumFlags = "0"  # Not enumerable, per spec.
                elif alias.startswith("@@"):
                    raise TypeError(
                        "Can't handle any well-known Symbol other than @@iterator and @@asyncIterator"
                    )
                else:
                    getSymbolJSID = None
                    defineFn = "JS_DefineProperty"
                    prop = '"%s"' % alias
                    # XXX If we ever create non-enumerable properties that can
                    #     be aliased, we should consider making the aliases
                    #     match the enumerability of the property being aliased.
                    enumFlags = "JSPROP_ENUMERATE"
                return CGList(
                    [
                        getSymbolJSID,
                        CGGeneric(
                            fill(
                                """
                        if (!${defineFn}(aCx, proto, ${prop}, aliasedVal, ${enumFlags})) {
                          $*{failureCode}
                        }
                        """,
                                defineFn=defineFn,
                                prop=prop,
                                enumFlags=enumFlags,
                                failureCode=failureCode,
                            )
                        ),
                    ],
                    "\n",
                )

            def defineAliasesFor(m):
                return CGList(
                    [
                        CGGeneric(
                            fill(
                                """
                        if (!JS_GetProperty(aCx, proto, \"${prop}\", &aliasedVal)) {
                          $*{failureCode}
                        }
                        """,
                                failureCode=failureCode,
                                prop=m.identifier.name,
                            )
                        )
                    ]
                    + [defineAlias(alias) for alias in sorted(m.aliases)]
                )

            defineAliases = CGList(
                [
                    CGGeneric(
                        dedent(
                            """
                    // Set up aliases on the interface prototype object we just created.
                    """
                        )
                    ),
                    CGGeneric("JS::Rooted<JS::Value> aliasedVal(aCx);\n\n"),
                ]
                + [
                    defineAliasesFor(m)
                    for m in sorted(aliasedMembers, key=lambda m: m.identifier.name)
                ]
            )
            needProtoVar = True
        else:
            defineAliases = None

        # Globals handle unforgeables directly in Wrap() instead of
        # via a holder.
        if (
            self.descriptor.hasLegacyUnforgeableMembers
            and not self.descriptor.isGlobal()
        ):
            assert needInterfacePrototypeObject

            # We want to use the same JSClass and prototype as the object we'll
            # end up defining the unforgeable properties on in the end, so that
            # we can use JS_InitializePropertiesFromCompatibleNativeObject to do
            # a fast copy.  In the case of proxies that's null, because the
            # expando object is a vanilla object, but in the case of other DOM
            # objects it's whatever our class is.
            if self.descriptor.proxy:
                holderClass = "nullptr"
                holderProto = "nullptr"
            else:
                holderClass = "sClass.ToJSClass()"
                holderProto = "proto"
                needProtoVar = True
            createUnforgeableHolder = CGGeneric(
                fill(
                    """
                JS::Rooted<JSObject*> unforgeableHolder(
                    aCx, JS_NewObjectWithoutMetadata(aCx, ${holderClass}, ${holderProto}));
                if (!unforgeableHolder) {
                  $*{failureCode}
                }
                """,
                    holderProto=holderProto,
                    holderClass=holderClass,
                    failureCode=failureCode,
                )
            )
            defineUnforgeables = InitUnforgeablePropertiesOnHolder(
                self.descriptor, self.properties, failureCode
            )
            createUnforgeableHolder = CGList(
                [createUnforgeableHolder, defineUnforgeables]
            )

            installUnforgeableHolder = CGGeneric(
                dedent(
                    """
                if (*protoCache) {
                  JS::SetReservedSlot(*protoCache, DOM_INTERFACE_PROTO_SLOTS_BASE,
                                      JS::ObjectValue(*unforgeableHolder));
                }
                """
                )
            )

            unforgeableHolderSetup = CGList(
                [createUnforgeableHolder, installUnforgeableHolder], "\n"
            )
        else:
            unforgeableHolderSetup = None

        if (
            self.descriptor.interface.isOnGlobalProtoChain()
            and needInterfacePrototypeObject
        ):
            makeProtoPrototypeImmutable = CGGeneric(
                fill(
                    """
                {
                  bool succeeded;
                  if (!JS_SetImmutablePrototype(aCx, proto, &succeeded)) {
                    $*{failureCode}
                  }

                  MOZ_ASSERT(succeeded,
                             "making a fresh prototype object's [[Prototype]] "
                             "immutable can internally fail, but it should "
                             "never be unsuccessful");
                }
                """,
                    protoCache=protoCache,
                    failureCode=failureCode,
                )
            )
            needProtoVar = True
        else:
            makeProtoPrototypeImmutable = None

        if needProtoVar:
            defineProtoVar = CGGeneric(
                fill(
                    """
                JS::AssertObjectIsNotGray(*protoCache);
                JS::Handle<JSObject*> proto = JS::Handle<JSObject*>::fromMarkedLocation(protoCache->unsafeAddress());
                if (!proto) {
                  $*{failureCode}
                }
                """,
                    failureCode=failureCode,
                )
            )
        else:
            defineProtoVar = None

        # ensureCaches needs to come first as it crashes on failure (like OOM).
        # We want to make sure that the caches do exist before we try to return
        # to the caller, so it can rely on that (and detect other failures by
        # checking for null in the caches).
        return CGList(
            [
                CGGeneric(ensureCaches),
                getParentProto,
                getConstructorProto,
                CGGeneric(call),
                defineProtoVar,
                defineAliases,
                unforgeableHolderSetup,
                makeProtoPrototypeImmutable,
            ],
            "\n",
        ).define()


class CGCreateAndDefineOnGlobalMethod(CGAbstractMethod):
    """
    A method for creating the interface or namespace object and defining
    properties for it on the global.
    """

    def __init__(self, descriptor):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "CreateAndDefineOnGlobal",
            "bool",
            [
                Argument("JSContext*", "aCx"),
            ],
            inline=True,
        )

    def definition_body(self):
        return fill(
            """
            // Get the interface or namespace object for this class. This will
            // create the object as needed and always define the properties for
            // it on the global. The caller should make sure the interface or
            // namespace is exposed on the global before calling this.
            return GetPerInterfaceObjectHandle(aCx, constructors::id::${name},
                                               &CreateInterfaceObjects,
                                               DefineInterfaceProperty::Always);

            """,
            name=self.descriptor.name,
        )


class CGGetProtoObjectHandleMethod(CGAbstractMethod):
    """
    A method for getting the interface prototype object.
    """

    def __init__(self, descriptor, static, signatureOnly=False):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "GetProtoObjectHandle",
            "JS::Handle<JSObject*>",
            [Argument("JSContext*", "aCx")],
            static=static,
            signatureOnly=signatureOnly,
        )

    def definition_body(self):
        return fill(
            """
            /* Get the interface prototype object for this class.  This will create the
               object as needed. */
            return GetPerInterfaceObjectHandle(aCx, prototypes::id::${name},
                                               &CreateInterfaceObjects,
                                               DefineInterfaceProperty::CheckExposure);

            """,
            name=self.descriptor.name,
        )


class CGGetProtoObjectMethod(CGAbstractMethod):
    """
    A method for getting the interface prototype object.
    """

    def __init__(self, descriptor):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "GetProtoObject",
            "JSObject*",
            [Argument("JSContext*", "aCx")],
        )

    def definition_body(self):
        return "return GetProtoObjectHandle(aCx);\n"


class CGGetConstructorObjectHandleMethod(CGAbstractMethod):
    """
    A method for getting the interface constructor object.
    """

    def __init__(self, descriptor):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "GetConstructorObjectHandle",
            "JS::Handle<JSObject*>",
            [
                Argument("JSContext*", "aCx"),
            ],
        )

    def definition_body(self):
        return fill(
            """
            /* Get the interface object for this class.  This will create the object as
               needed. */

            return GetPerInterfaceObjectHandle(aCx, constructors::id::${name},
                                               &CreateInterfaceObjects,
                                               DefineInterfaceProperty::CheckExposure);
            """,
            name=self.descriptor.name,
        )


class CGGetNamedPropertiesObjectMethod(CGAbstractStaticMethod):
    def __init__(self, descriptor):
        args = [Argument("JSContext*", "aCx")]
        CGAbstractStaticMethod.__init__(
            self, descriptor, "GetNamedPropertiesObject", "JSObject*", args
        )

    def definition_body(self):
        parentProtoName = self.descriptor.parentPrototypeName
        if parentProtoName is None:
            getParentProto = ""
            parentProto = "nullptr"
        else:
            getParentProto = fill(
                """
                JS::Rooted<JSObject*> parentProto(aCx, ${parent}::GetProtoObjectHandle(aCx));
                if (!parentProto) {
                  return nullptr;
                }
                """,
                parent=toBindingNamespace(parentProtoName),
            )
            parentProto = "parentProto"
        return fill(
            """
            /* Make sure our global is sane.  Hopefully we can remove this sometime */
            JSObject* global = JS::CurrentGlobalOrNull(aCx);
            if (!(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL)) {
              return nullptr;
            }

            /* Check to see whether the named properties object has already been created */
            ProtoAndIfaceCache& protoAndIfaceCache = *GetProtoAndIfaceCache(global);

            JS::Heap<JSObject*>& namedPropertiesObject = protoAndIfaceCache.EntrySlotOrCreate(namedpropertiesobjects::id::${ifaceName});
            if (!namedPropertiesObject) {
              $*{getParentProto}
              namedPropertiesObject = ${nativeType}::CreateNamedPropertiesObject(aCx, ${parentProto});
              DebugOnly<const DOMIfaceAndProtoJSClass*> clasp =
                DOMIfaceAndProtoJSClass::FromJSClass(JS::GetClass(namedPropertiesObject));
              MOZ_ASSERT(clasp->mType == eNamedPropertiesObject,
                         "Expected ${nativeType}::CreateNamedPropertiesObject to return a named properties object");
              MOZ_ASSERT(clasp->mNativeHooks,
                         "The named properties object for ${nativeType} should have NativePropertyHooks.");
              MOZ_ASSERT(!clasp->mNativeHooks->mIndexedOrNamedNativeProperties ||
                         !clasp->mNativeHooks->mIndexedOrNamedNativeProperties->mResolveOwnProperty,
                         "Shouldn't resolve the properties of the named properties object for ${nativeType} for Xrays.");
              MOZ_ASSERT(!clasp->mNativeHooks->mIndexedOrNamedNativeProperties ||
                         !clasp->mNativeHooks->mIndexedOrNamedNativeProperties->mEnumerateOwnProperties,
                         "Shouldn't enumerate the properties of the named properties object for ${nativeType} for Xrays.");
            }
            return namedPropertiesObject.get();
            """,
            getParentProto=getParentProto,
            ifaceName=self.descriptor.name,
            parentProto=parentProto,
            nativeType=self.descriptor.nativeType,
        )


def getRawConditionList(idlobj, cxName, objName, ignoreSecureContext=False):
    """
    Get the list of conditions for idlobj (to be used in "is this enabled"
    checks).  This will be returned as a CGList with " &&\n" as the separator,
    for readability.

    objName is the name of the object that we're working with, because some of
    our test functions want that.

    ignoreSecureContext is used only for constructors in which the WebIDL interface
    itself is already marked as [SecureContext]. There is no need to do the work twice.
    """
    conditions = []
    pref = idlobj.getExtendedAttribute("Pref")
    if pref:
        assert isinstance(pref, list) and len(pref) == 1
        conditions.append("StaticPrefs::%s()" % prefIdentifier(pref[0]))
    if isChromeOnly(idlobj):
        conditions.append("nsContentUtils::ThreadsafeIsSystemCaller(%s)" % cxName)
    func = idlobj.getExtendedAttribute("Func")
    if func:
        assert isinstance(func, list) and len(func) == 1
        conditions.append("%s(%s, %s)" % (func[0], cxName, objName))
    trial = idlobj.getExtendedAttribute("Trial")
    if trial:
        assert isinstance(trial, list) and len(trial) == 1
        conditions.append(
            "OriginTrials::IsEnabled(%s, %s, OriginTrial::%s)"
            % (cxName, objName, trial[0])
        )
    if not ignoreSecureContext and idlobj.getExtendedAttribute("SecureContext"):
        conditions.append(
            "mozilla::dom::IsSecureContextOrObjectIsFromSecureContext(%s, %s)"
            % (cxName, objName)
        )
    return conditions


def getConditionList(idlobj, cxName, objName, ignoreSecureContext=False):
    """
    Get the list of conditions from getRawConditionList
    See comment on getRawConditionList above for more info about arguments.

    The return value is a possibly-empty conjunctive CGList of conditions.
    """
    conditions = getRawConditionList(idlobj, cxName, objName, ignoreSecureContext)
    return CGList((CGGeneric(cond) for cond in conditions), " &&\n")


class CGConstructorEnabled(CGAbstractMethod):
    """
    A method for testing whether we should be exposing this interface object.
    This can perform various tests depending on what conditions are specified
    on the interface.
    """

    def __init__(self, descriptor):
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "ConstructorEnabled",
            "bool",
            [Argument("JSContext*", "aCx"), Argument("JS::Handle<JSObject*>", "aObj")],
        )

    def definition_body(self):
        body = CGList([], "\n")

        iface = self.descriptor.interface

        if not iface.isExposedInWindow():
            exposedInWindowCheck = dedent(
                """
                MOZ_ASSERT(!NS_IsMainThread(), "Why did we even get called?");
                """
            )
            body.append(CGGeneric(exposedInWindowCheck))

        if iface.isExposedInSomeButNotAllWorkers():
            workerGlobals = sorted(iface.getWorkerExposureSet())
            workerCondition = CGList(
                (
                    CGGeneric('strcmp(name, "%s")' % workerGlobal)
                    for workerGlobal in workerGlobals
                ),
                " && ",
            )
            exposedInWorkerCheck = fill(
                """
                const char* name = JS::GetClass(aObj)->name;
                if (${workerCondition}) {
                  return false;
                }
                """,
                workerCondition=workerCondition.define(),
            )
            exposedInWorkerCheck = CGGeneric(exposedInWorkerCheck)
            if iface.isExposedInWindow():
                exposedInWorkerCheck = CGIfWrapper(
                    exposedInWorkerCheck, "!NS_IsMainThread()"
                )
            body.append(exposedInWorkerCheck)

        conditions = getConditionList(iface, "aCx", "aObj")

        # We should really have some conditions
        assert len(body) or len(conditions)

        conditionsWrapper = ""
        if len(conditions):
            conditionsWrapper = CGWrapper(
                conditions, pre="return ", post=";\n", reindent=True
            )
        else:
            conditionsWrapper = CGGeneric("return true;\n")

        body.append(conditionsWrapper)
        return body.define()


def StructuredCloneTag(name):
    return "SCTAG_DOM_%s" % name.upper()


class CGSerializer(CGAbstractStaticMethod):
    """
    Implementation of serialization for things marked [Serializable].
    This gets stored in our DOMJSClass, so it can be static.

    The caller is expected to pass in the object whose DOMJSClass it
    used to get the serializer.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("JSStructuredCloneWriter*", "aWriter"),
            Argument("JS::Handle<JSObject*>", "aObj"),
        ]
        CGAbstractStaticMethod.__init__(self, descriptor, "Serialize", "bool", args)

    def definition_body(self):
        return fill(
            """
            MOZ_ASSERT(IsDOMObject(aObj), "Non-DOM object passed");
            MOZ_ASSERT(GetDOMClass(aObj)->mSerializer == &Serialize,
                       "Wrong object passed");
            return JS_WriteUint32Pair(aWriter, ${tag}, 0) &&
                   UnwrapDOMObject<${type}>(aObj)->WriteStructuredClone(aCx, aWriter);
            """,
            tag=StructuredCloneTag(self.descriptor.name),
            type=self.descriptor.nativeType,
        )


class CGDeserializer(CGAbstractMethod):
    """
    Implementation of deserialization for things marked [Serializable].
    This will need to be accessed from WebIDLSerializable, so can't be static.
    """

    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("nsIGlobalObject*", "aGlobal"),
            Argument("JSStructuredCloneReader*", "aReader"),
        ]
        CGAbstractMethod.__init__(self, descriptor, "Deserialize", "JSObject*", args)

    def definition_body(self):
        # WrapObject has different signatures depending on whether
        # the object is wrappercached.
        if self.descriptor.wrapperCache:
            wrapCall = dedent(
                """
                result = obj->WrapObject(aCx, nullptr);
                if (!result) {
                  return nullptr;
                }
                """
            )
        else:
            wrapCall = dedent(
                """
                if (!obj->WrapObject(aCx, nullptr, &result)) {
                  return nullptr;
                }
                """
            )

        return fill(
            """
            // Protect the result from a moving GC in ~RefPtr
            JS::Rooted<JSObject*> result(aCx);
            {  // Scope for the RefPtr
              RefPtr<${type}> obj = ${type}::ReadStructuredClone(aCx, aGlobal, aReader);
              if (!obj) {
                return nullptr;
              }
              $*{wrapCall}
            }
            return result;
            """,
            type=self.descriptor.nativeType,
            wrapCall=wrapCall,
        )


def CreateBindingJSObject(descriptor):
    objDecl = "BindingJSObjectCreator<%s> creator(aCx);\n" % descriptor.nativeType

    # We don't always need to root obj, but there are a variety
    # of cases where we do, so for simplicity, just always root it.
    if descriptor.proxy:
        if descriptor.interface.getExtendedAttribute("LegacyOverrideBuiltIns"):
            assert not descriptor.isMaybeCrossOriginObject()
            create = dedent(
                """
                aObject->mExpandoAndGeneration.expando.setUndefined();
                JS::Rooted<JS::Value> expandoValue(aCx, JS::PrivateValue(&aObject->mExpandoAndGeneration));
                creator.CreateProxyObject(aCx, &sClass.mBase, DOMProxyHandler::getInstance(),
                                          proto, /* aLazyProto = */ false, aObject,
                                          expandoValue, aReflector);
                """
            )
        else:
            if descriptor.isMaybeCrossOriginObject():
                proto = "nullptr"
                lazyProto = "true"
            else:
                proto = "proto"
                lazyProto = "false"
            create = fill(
                """
                creator.CreateProxyObject(aCx, &sClass.mBase, DOMProxyHandler::getInstance(),
                                          ${proto}, /* aLazyProto = */ ${lazyProto},
                                          aObject, JS::UndefinedHandleValue, aReflector);
                """,
                proto=proto,
                lazyProto=lazyProto,
            )
    else:
        create = dedent(
            """
            creator.CreateObject(aCx, sClass.ToJSClass(), proto, aObject, aReflector);
            """
        )
    return (
        objDecl
        + create
        + dedent(
            """
        if (!aReflector) {
          return false;
        }
        """
        )
    )


def InitUnforgeablePropertiesOnHolder(
    descriptor, properties, failureCode, holderName="unforgeableHolder"
):
    """
    Define the unforgeable properties on the unforgeable holder for
    the interface represented by descriptor.

    properties is a PropertyArrays instance.

    """
    assert (
        properties.unforgeableAttrs.hasNonChromeOnly()
        or properties.unforgeableAttrs.hasChromeOnly()
        or properties.unforgeableMethods.hasNonChromeOnly()
        or properties.unforgeableMethods.hasChromeOnly()
    )

    unforgeables = []

    defineUnforgeableAttrs = fill(
        """
        if (!DefineLegacyUnforgeableAttributes(aCx, ${holderName}, %s)) {
          $*{failureCode}
        }
        """,
        failureCode=failureCode,
        holderName=holderName,
    )
    defineUnforgeableMethods = fill(
        """
        if (!DefineLegacyUnforgeableMethods(aCx, ${holderName}, %s)) {
          $*{failureCode}
        }
        """,
        failureCode=failureCode,
        holderName=holderName,
    )

    unforgeableMembers = [
        (defineUnforgeableAttrs, properties.unforgeableAttrs),
        (defineUnforgeableMethods, properties.unforgeableMethods),
    ]
    for template, array in unforgeableMembers:
        if array.hasNonChromeOnly():
            unforgeables.append(CGGeneric(template % array.variableName(False)))
        if array.hasChromeOnly():
            unforgeables.append(
                CGIfWrapper(
                    CGGeneric(template % array.variableName(True)),
                    "nsContentUtils::ThreadsafeIsSystemCaller(aCx)",
                )
            )

    if descriptor.interface.getExtendedAttribute("LegacyUnforgeable"):
        # We do our undefined toPrimitive here, not as a regular property
        # because we don't have a concept of value props anywhere in IDL.
        unforgeables.append(
            CGGeneric(
                fill(
                    """
            JS::Rooted<JS::PropertyKey> toPrimitive(aCx,
              JS::GetWellKnownSymbolKey(aCx, JS::SymbolCode::toPrimitive));
            if (!JS_DefinePropertyById(aCx, ${holderName}, toPrimitive,
                                       JS::UndefinedHandleValue,
                                       JSPROP_READONLY | JSPROP_PERMANENT)) {
              $*{failureCode}
            }
            """,
                    failureCode=failureCode,
                    holderName=holderName,
                )
            )
        )

    return CGWrapper(CGList(unforgeables), pre="\n")


def CopyUnforgeablePropertiesToInstance(descriptor, failureCode):
    """
    Copy the unforgeable properties from the unforgeable holder for
    this interface to the instance object we have.
    """
    assert not descriptor.isGlobal()

    if not descriptor.hasLegacyUnforgeableMembers:
        return ""

    copyCode = [
        CGGeneric(
            dedent(
                """
            // Important: do unforgeable property setup after we have handed
            // over ownership of the C++ object to obj as needed, so that if
            // we fail and it ends up GCed it won't have problems in the
            // finalizer trying to drop its ownership of the C++ object.
            """
            )
        )
    ]

    # For proxies, we want to define on the expando object, not directly on the
    # reflector, so we can make sure we don't get confused by named getters.
    if descriptor.proxy:
        copyCode.append(
            CGGeneric(
                fill(
                    """
            JS::Rooted<JSObject*> expando(aCx,
              DOMProxyHandler::EnsureExpandoObject(aCx, aReflector));
            if (!expando) {
              $*{failureCode}
            }
            """,
                    failureCode=failureCode,
                )
            )
        )
        obj = "expando"
    else:
        obj = "aReflector"

    copyCode.append(
        CGGeneric(
            fill(
                """
        JS::Rooted<JSObject*> unforgeableHolder(aCx,
          &JS::GetReservedSlot(canonicalProto, DOM_INTERFACE_PROTO_SLOTS_BASE).toObject());
        if (!JS_InitializePropertiesFromCompatibleNativeObject(aCx, ${obj}, unforgeableHolder)) {
          $*{failureCode}
        }
        """,
                obj=obj,
                failureCode=failureCode,
            )
        )
    )

    return CGWrapper(CGList(copyCode), pre="\n").define()


def AssertInheritanceChain(descriptor):
    # We can skip the reinterpret_cast check for the descriptor's nativeType
    # if aObject is a pointer of that type.
    asserts = fill(
        """
        static_assert(std::is_same_v<decltype(aObject), ${nativeType}*>);
        """,
        nativeType=descriptor.nativeType,
    )
    iface = descriptor.interface
    while iface.parent:
        iface = iface.parent
        desc = descriptor.getDescriptor(iface.identifier.name)
        asserts += (
            "MOZ_ASSERT(static_cast<%s*>(aObject) == \n"
            "           reinterpret_cast<%s*>(aObject),\n"
            '           "Multiple inheritance for %s is broken.");\n'
            % (desc.nativeType, desc.nativeType, desc.nativeType)
        )
    asserts += "MOZ_ASSERT(ToSupportsIsCorrect(aObject));\n"
    return asserts


def InitMemberSlots(descriptor, failureCode):
    """
    Initialize member slots on our JS object if we're supposed to have some.

    Note that this is called after the SetWrapper() call in the
    wrapperCache case, since that can affect how our getters behave
    and we plan to invoke them here.  So if we fail, we need to
    ClearWrapper.
    """
    if not descriptor.interface.hasMembersInSlots():
        return ""
    return fill(
        """
        if (!UpdateMemberSlots(aCx, aReflector, aObject)) {
          $*{failureCode}
        }
        """,
        failureCode=failureCode,
    )


def DeclareProto(descriptor, noGivenProto=False):
    """
    Declare the canonicalProto and proto we have for our wrapping operation.
    """
    getCanonical = dedent(
        """
        JS::Handle<JSObject*> ${canonicalProto} = GetProtoObjectHandle(aCx);
        if (!${canonicalProto}) {
          return false;
        }
        """
    )

    if noGivenProto:
        return fill(getCanonical, canonicalProto="proto")

    getCanonical = fill(getCanonical, canonicalProto="canonicalProto")

    preamble = getCanonical + dedent(
        """
        JS::Rooted<JSObject*> proto(aCx);
        """
    )
    if descriptor.isMaybeCrossOriginObject():
        return preamble + dedent(
            """
            MOZ_ASSERT(!aGivenProto,
                       "Shouldn't have constructors on cross-origin objects");
            // Set proto to canonicalProto to avoid preserving our wrapper if
            // we don't have to.
            proto = canonicalProto;
            """
        )

    return preamble + dedent(
        """
        if (aGivenProto) {
          proto = aGivenProto;
          // Unfortunately, while aGivenProto was in the compartment of aCx
          // coming in, we changed compartments to that of "parent" so may need
          // to wrap the proto here.
          if (js::GetContextCompartment(aCx) != JS::GetCompartment(proto)) {
            if (!JS_WrapObject(aCx, &proto)) {
              return false;
            }
          }
        } else {
          proto = canonicalProto;
        }
        """
    )


class CGWrapWithCacheMethod(CGAbstractMethod):
    """
    Create a wrapper JSObject for a given native that implements nsWrapperCache.
    """

    def __init__(self, descriptor):
        assert descriptor.interface.hasInterfacePrototypeObject()
        args = [
            Argument("JSContext*", "aCx"),
            Argument(descriptor.nativeType + "*", "aObject"),
            Argument("nsWrapperCache*", "aCache"),
            Argument("JS::Handle<JSObject*>", "aGivenProto"),
            Argument("JS::MutableHandle<JSObject*>", "aReflector"),
        ]
        CGAbstractMethod.__init__(self, descriptor, "Wrap", "bool", args)

    def definition_body(self):
        failureCode = dedent(
            """
            aCache->ReleaseWrapper(aObject);
            aCache->ClearWrapper();
            return false;
            """
        )

        if self.descriptor.proxy:
            finalize = "DOMProxyHandler::getInstance()->finalize"
        else:
            finalize = FINALIZE_HOOK_NAME

        return fill(
            """
            static_assert(!std::is_base_of_v<NonRefcountedDOMObject, ${nativeType}>,
                          "Shouldn't have wrappercached things that are not refcounted.");
            $*{assertInheritance}
            MOZ_ASSERT_IF(aGivenProto, js::IsObjectInContextCompartment(aGivenProto, aCx));
            MOZ_ASSERT(!aCache->GetWrapper(),
                       "You should probably not be using Wrap() directly; use "
                       "GetOrCreateDOMReflector instead");

            MOZ_ASSERT(ToSupportsIsOnPrimaryInheritanceChain(aObject, aCache),
                       "nsISupports must be on our primary inheritance chain");

            // If the wrapper cache contains a dead reflector then finalize that
            // now, ensuring that the finalizer for the old reflector always
            // runs before the new reflector is created and attached. This
            // avoids the awkward situation where there are multiple reflector
            // objects that contain pointers to the same native.

            if (JSObject* oldReflector = aCache->GetWrapperMaybeDead()) {
              ${finalize}(nullptr /* unused */, oldReflector);
              MOZ_ASSERT(!aCache->GetWrapperMaybeDead());
            }

            JS::Rooted<JSObject*> global(aCx, FindAssociatedGlobal(aCx, aObject->GetParentObject()));
            if (!global) {
              return false;
            }
            MOZ_ASSERT(JS_IsGlobalObject(global));
            JS::AssertObjectIsNotGray(global);

            // That might have ended up wrapping us already, due to the wonders
            // of XBL.  Check for that, and bail out as needed.
            aReflector.set(aCache->GetWrapper());
            if (aReflector) {
            #ifdef DEBUG
              AssertReflectorHasGivenProto(aCx, aReflector, aGivenProto);
            #endif // DEBUG
              return true;
            }

            JSAutoRealm ar(aCx, global);
            $*{declareProto}

            $*{createObject}

            aCache->SetWrapper(aReflector);
            $*{unforgeable}
            $*{slots}
            creator.InitializationSucceeded();

            MOZ_ASSERT(aCache->GetWrapperPreserveColor() &&
                       aCache->GetWrapperPreserveColor() == aReflector);
            // If proto != canonicalProto, we have to preserve our wrapper;
            // otherwise we won't be able to properly recreate it later, since
            // we won't know what proto to use.  Note that we don't check
            // aGivenProto here, since it's entirely possible (and even
            // somewhat common) to have a non-null aGivenProto which is the
            // same as canonicalProto.
            if (proto != canonicalProto) {
              PreserveWrapper(aObject);
            }

            return true;
            """,
            nativeType=self.descriptor.nativeType,
            assertInheritance=AssertInheritanceChain(self.descriptor),
            declareProto=DeclareProto(self.descriptor),
            createObject=CreateBindingJSObject(self.descriptor),
            unforgeable=CopyUnforgeablePropertiesToInstance(
                self.descriptor, failureCode
            ),
            slots=InitMemberSlots(self.descriptor, failureCode),
            finalize=finalize,
        )


class CGWrapMethod(CGAbstractMethod):
    def __init__(self, descriptor):
        # XXX can we wrap if we don't have an interface prototype object?
        assert descriptor.interface.hasInterfacePrototypeObject()
        args = [
            Argument("JSContext*", "aCx"),
            Argument("T*", "aObject"),
            Argument("JS::Handle<JSObject*>", "aGivenProto"),
        ]
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "Wrap",
            "JSObject*",
            args,
            inline=True,
            templateArgs=["class T"],
        )

    def definition_body(self):
        return dedent(
            """
            JS::Rooted<JSObject*> reflector(aCx);
            return Wrap(aCx, aObject, aObject, aGivenProto, &reflector) ? reflector.get() : nullptr;
            """
        )


class CGWrapNonWrapperCacheMethod(CGAbstractMethod):
    """
    Create a wrapper JSObject for a given native that does not implement
    nsWrapperCache.
    """

    def __init__(self, descriptor, static=False, signatureOnly=False):
        # XXX can we wrap if we don't have an interface prototype object?
        assert descriptor.interface.hasInterfacePrototypeObject()
        self.noGivenProto = (
            descriptor.interface.isIteratorInterface()
            or descriptor.interface.isAsyncIteratorInterface()
        )
        args = [
            Argument("JSContext*", "aCx"),
            Argument(descriptor.nativeType + "*", "aObject"),
        ]
        if not self.noGivenProto:
            args.append(Argument("JS::Handle<JSObject*>", "aGivenProto"))
        args.append(Argument("JS::MutableHandle<JSObject*>", "aReflector"))
        CGAbstractMethod.__init__(
            self,
            descriptor,
            "Wrap",
            "bool",
            args,
            static=static,
            signatureOnly=signatureOnly,
        )

    def definition_body(self):
        failureCode = "return false;\n"

        declareProto = DeclareProto(self.descriptor, noGivenProto=self.noGivenProto)
        if self.noGivenProto:
            assertGivenProto = ""
        else:
            assertGivenProto = dedent(
                """
                MOZ_ASSERT_IF(aGivenProto, js::IsObjectInContextCompartment(aGivenProto, aCx));
                """
            )
        return fill(
            """
            $*{assertions}
            $*{assertGivenProto}

            JS::Rooted<JSObject*> global(aCx, JS::CurrentGlobalOrNull(aCx));
            $*{declareProto}

            $*{createObject}

            $*{unforgeable}

            $*{slots}

            creator.InitializationSucceeded();
            return true;
            """,
            assertions=AssertInheritanceChain(self.descriptor),
            assertGivenProto=assertGivenProto,
            declareProto=declareProto,
            createObject=CreateBindingJSObject(self.descriptor),
            unforgeable=CopyUnforgeablePropertiesToInstance(
                self.descriptor, failureCode
            ),
            slots=InitMemberSlots(self.descriptor, failureCode),
        )


class CGWrapGlobalMethod(CGAbstractMethod):
    """
    Create a wrapper JSObject for a global.  The global must implement
    nsWrapperCache.

    properties should be a PropertyArrays instance.
    """

    def __init__(self, descriptor, properties):
        assert (
            descriptor.interface.hasInterfacePrototypeObject()
            or descriptor.hasOrdinaryObjectPrototype()
        )
        args = [
            Argument("JSContext*", "aCx"),
            Argument(descriptor.nativeType + "*", "aObject"),
            Argument("nsWrapperCache*", "aCache"),
            Argument("JS::RealmOptions&", "aOptions"),
            Argument("JSPrincipals*", "aPrincipal"),
            Argument("JS::MutableHandle<JSObject*>", "aReflector"),
        ]
        CGAbstractMethod.__init__(self, descriptor, "Wrap", "bool", args)
        self.descriptor = descriptor
        self.properties = properties

    def definition_body(self):
        if self.properties.hasNonChromeOnly():
            properties = "sNativeProperties.Upcast()"
        else:
            properties = "nullptr"
        if self.properties.hasChromeOnly():
            chromeProperties = "nsContentUtils::ThreadsafeIsSystemCaller(aCx) ? sChromeOnlyNativeProperties.Upcast() : nullptr"
        else:
            chromeProperties = "nullptr"

        failureCode = dedent(
            """
            aCache->ReleaseWrapper(aObject);
            aCache->ClearWrapper();
            return false;
            """
        )

        if self.descriptor.hasLegacyUnforgeableMembers:
            unforgeable = InitUnforgeablePropertiesOnHolder(
                self.descriptor, self.properties, failureCode, "aReflector"
            ).define()
        else:
            unforgeable = ""

        if self.descriptor.hasOrdinaryObjectPrototype():
            getProto = "JS::GetRealmObjectPrototypeHandle"
        else:
            getProto = "GetProtoObjectHandle"
        return fill(
            """
            $*{assertions}
            MOZ_ASSERT(ToSupportsIsOnPrimaryInheritanceChain(aObject, aCache),
                       "nsISupports must be on our primary inheritance chain");

            if (!CreateGlobal<${nativeType}, ${getProto}>(aCx,
                                             aObject,
                                             aCache,
                                             sClass.ToJSClass(),
                                             aOptions,
                                             aPrincipal,
                                             aReflector)) {
              $*{failureCode}
            }

            // aReflector is a new global, so has a new realm.  Enter it
            // before doing anything with it.
            JSAutoRealm ar(aCx, aReflector);

            if (!DefineProperties(aCx, aReflector, ${properties}, ${chromeProperties})) {
              $*{failureCode}
            }
            $*{unforgeable}

            $*{slots}

            return true;
            """,
            assertions=AssertInheritanceChain(self.descriptor),
            nativeType=self.descriptor.nativeType,
            getProto=getProto,
            properties=properties,
            chromeProperties=chromeProperties,
            failureCode=failureCode,
            unforgeable=unforgeable,
            slots=InitMemberSlots(self.descriptor, failureCode),
        )


class CGUpdateMemberSlotsMethod(CGAbstractStaticMethod):
    def __init__(self, descriptor):
        args = [
            Argument("JSContext*", "aCx"),
            Argument("JS::Handle<JSObject*>", "aWrapper"),
            Argument(descriptor.nativeType + "*", "aObject"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, "UpdateMemberSlots", "bool", args
        )

    def definition_body(self):
        body = "JS::Rooted<JS::Value> temp(aCx);\n" "JSJitGetterCallArgs args(&temp);\n"
        for m in self.descriptor.interface.members:
            if m.isAttr() and m.getExtendedAttribute("StoreInSlot"):
                # Skip doing this for the "window" and "self" attributes on the
                # Window interface, because those can't be gotten safely until
                # we have hooked it up correctly to the outer window.  The
                # window code handles doing the get itself.
                if self.descriptor.interface.identifier.name == "Window" and (
                    m.identifier.name == "window" or m.identifier.name == "self"
                ):
                    continue
                body += fill(
                    """

                    static_assert(${slot} < JS::shadow::Object::MAX_FIXED_SLOTS,
                                  "Not enough fixed slots to fit '${interface}.${member}.  Ion's visitGetDOMMemberV/visitGetDOMMemberT assume StoreInSlot things are all in fixed slots.");
                    if (!get_${member}(aCx, aWrapper, aObject, args)) {
                      return false;
                    }
                    // Getter handled setting our reserved slots
                    """,
                    slot=memberReservedSlot(m, self.descriptor),
                    interface=self.descriptor.interface.identifier.name,
                    member=m.identifier.name,
                )

        body += "\nreturn true;\n"
        return body


class CGClearCachedValueMethod(CGAbstractMethod):
    def __init__(self, descriptor, member):
        self.member = member
        # If we're StoreInSlot, we'll need to call the getter
        if member.getExtendedAttribute("StoreInSlot"):
            args = [Argument("JSContext*", "aCx")]
            returnType = "bool"
        else:
            args = []
            returnType = "void"
        args.append(Argument(descriptor.nativeType + "*", "aObject"))
        name = MakeClearCachedValueNativeName(member)
        CGAbstractMethod.__init__(self, descriptor, name, returnType, args)

    def definition_body(self):
        slotIndex = memberReservedSlot(self.member, self.descriptor)
        clearCachedValue = fill(
            """
            JS::SetReservedSlot(obj, ${slotIndex}, JS::UndefinedValue());
            """,
            slotIndex=slotIndex,
        )
        if self.member.getExtendedAttribute("StoreInSlot"):
            # We have to root things and save the old value in case
            # regetting fails, so we can restore it.
            declObj = "JS::Rooted<JSObject*> obj(aCx);\n"
            noopRetval = " true"
            saveMember = (
                "JS::Rooted<JS::Value> oldValue(aCx, JS::GetReservedSlot(obj, %s));\n"
                % slotIndex
            )
            regetMember = fill(
                """
                JS::Rooted<JS::Value> temp(aCx);
                JSJitGetterCallArgs args(&temp);
                JSAutoRealm ar(aCx, obj);
                if (!get_${name}(aCx, obj, aObject, args)) {
                  JS::SetReservedSlot(obj, ${slotIndex}, oldValue);
                  return false;
                }
                return true;
                """,
                name=self.member.identifier.name,
                slotIndex=slotIndex,
            )
        else:
            declObj = "JSObject* obj;\n"
            noopRetval = ""
            saveMember = ""
            if self.member.getExtendedAttribute(
                "ReflectedHTMLAttributeReturningFrozenArray"
            ):
                clearCachedValue = fill(
                    """
                    ReflectedHTMLAttributeSlots::Clear(obj, ${arrayIndex});
                    """,
                    arrayIndex=reflectedHTMLAttributesArrayIndex(
                        self.descriptor, self.member
                    ),
                )
            regetMember = ""

        if self.descriptor.wantsXrays:
            if self.member.getExtendedAttribute("StoreInSlot"):
                cx = "JS::RootingContext::get(aCx)"
            else:
                cx = "RootingCx()"
            if self.member.getExtendedAttribute(
                "ReflectedHTMLAttributeReturningFrozenArray"
            ):
                clearXrayExpandoSlots = fill(
                    """
                    ReflectedHTMLAttributeSlots::ClearInXrays(${cx}, obj, ${arrayIndex});
                    """,
                    cx=cx,
                    arrayIndex=reflectedHTMLAttributesArrayIndex(
                        self.descriptor, self.member
                    ),
                )
            else:
                clearXrayExpandoSlots = fill(
                    """
                    ClearXrayExpandoSlots(${cx}, obj, ${xraySlotIndex});
                    """,
                    cx=cx,
                    xraySlotIndex=memberXrayExpandoReservedSlot(
                        self.member, self.descriptor
                    ),
                )
        else:
            clearXrayExpandoSlots = ""

        return fill(
            """
            $*{declObj}
            obj = aObject->GetWrapper();
            if (!obj) {
              return${noopRetval};
            }
            $*{saveMember}
            $*{clearCachedValue}
            $*{clearXrayExpandoSlots}
            $*{regetMember}
            """,
            declObj=declObj,
            noopRetval=noopRetval,
            saveMember=saveMember,
            slotIndex=slotIndex,
            clearCachedValue=clearCachedValue,
            clearXrayExpandoSlots=clearXrayExpandoSlots,
            regetMember=regetMember,
        )


class CGCrossOriginProperties(CGThing):
    def __init__(self, descriptor):
        attrs = []
        chromeOnlyAttrs = []
        methods = []
        chromeOnlyMethods = []
        for m in descriptor.interface.members:
            if m.isAttr() and (
                m.getExtendedAttribute("CrossOriginReadable")
                or m.getExtendedAttribute("CrossOriginWritable")
            ):
                if m.isStatic():
                    raise TypeError(
                        "Don't know how to deal with static method %s"
                        % m.identifier.name
                    )
                if PropertyDefiner.getControllingCondition(
                    m, descriptor
                ).hasDisablers():
                    raise TypeError(
                        "Don't know how to deal with disabler for %s"
                        % m.identifier.name
                    )
                if len(m.bindingAliases) > 0:
                    raise TypeError(
                        "Don't know how to deal with aliases for %s" % m.identifier.name
                    )
                if m.getExtendedAttribute("ChromeOnly") is not None:
                    chromeOnlyAttrs.extend(AttrDefiner.attrData(m, overrideFlags="0"))
                else:
                    attrs.extend(AttrDefiner.attrData(m, overrideFlags="0"))
            elif m.isMethod() and m.getExtendedAttribute("CrossOriginCallable"):
                if m.isStatic():
                    raise TypeError(
                        "Don't know how to deal with static method %s"
                        % m.identifier.name
                    )
                if PropertyDefiner.getControllingCondition(
                    m, descriptor
                ).hasDisablers():
                    raise TypeError(
                        "Don't know how to deal with disabler for %s"
                        % m.identifier.name
                    )
                if len(m.aliases) > 0:
                    raise TypeError(
                        "Don't know how to deal with aliases for %s" % m.identifier.name
                    )
                if m.getExtendedAttribute("ChromeOnly") is not None:
                    chromeOnlyMethods.append(
                        MethodDefiner.methodData(
                            m, descriptor, overrideFlags="JSPROP_READONLY"
                        )
                    )
                else:
                    methods.append(
                        MethodDefiner.methodData(
                            m, descriptor, overrideFlags="JSPROP_READONLY"
                        )
                    )

        if len(attrs) > 0:
            self.attributeSpecs, _ = PropertyDefiner.generatePrefableArrayValues(
                attrs,
                descriptor,
                AttrDefiner.formatSpec,
                "  JS_PS_END\n",
                AttrDefiner.condition,
                functools.partial(AttrDefiner.specData, crossOriginOnly=True),
            )
        else:
            self.attributeSpecs = [" JS_PS_END\n"]
        if len(methods) > 0:
            self.methodSpecs, _ = PropertyDefiner.generatePrefableArrayValues(
                methods,
                descriptor,
                MethodDefiner.formatSpec,
                "  JS_FS_END\n",
                MethodDefiner.condition,
                MethodDefiner.specData,
            )
        else:
            self.methodSpecs = ["  JS_FS_END\n"]

        if len(chromeOnlyAttrs) > 0:
            (
                self.chromeOnlyAttributeSpecs,
                _,
            ) = PropertyDefiner.generatePrefableArrayValues(
                chromeOnlyAttrs,
                descriptor,
                AttrDefiner.formatSpec,
                "  JS_PS_END\n",
                AttrDefiner.condition,
                functools.partial(AttrDefiner.specData, crossOriginOnly=True),
            )
        else:
            self.chromeOnlyAttributeSpecs = []
        if len(chromeOnlyMethods) > 0:
            self.chromeOnlyMethodSpecs, _ = PropertyDefiner.generatePrefableArrayValues(
                chromeOnlyMethods,
                descriptor,
                MethodDefiner.formatSpec,
                "  JS_FS_END\n",
                MethodDefiner.condition,
                MethodDefiner.specData,
            )
        else:
            self.chromeOnlyMethodSpecs = []

    def declare(self):
        return dedent(
            """
            extern const CrossOriginProperties sCrossOriginProperties;
            """
        )

    def define(self):
        def defineChromeOnly(name, specs, specType):
            if len(specs) == 0:
                return ("", "nullptr")
            name = "sChromeOnlyCrossOrigin" + name
            define = fill(
                """
                static const ${specType} ${name}[] = {
                  $*{specs}
                };
                """,
                specType=specType,
                name=name,
                specs=",\n".join(specs),
            )
            return (define, name)

        chromeOnlyAttributes = defineChromeOnly(
            "Attributes", self.chromeOnlyAttributeSpecs, "JSPropertySpec"
        )
        chromeOnlyMethods = defineChromeOnly(
            "Methods", self.chromeOnlyMethodSpecs, "JSFunctionSpec"
        )
        return fill(
            """
            static const JSPropertySpec sCrossOriginAttributes[] = {
              $*{attributeSpecs}
            };
            static const JSFunctionSpec sCrossOriginMethods[] = {
              $*{methodSpecs}
            };
            $*{chromeOnlyAttributeSpecs}
            $*{chromeOnlyMethodSpecs}
            const CrossOriginProperties sCrossOriginProperties = {
              sCrossOriginAttributes,
              sCrossOriginMethods,
              ${chromeOnlyAttributes},
              ${chromeOnlyMethods}
            };
            """,
            attributeSpecs=",\n".join(self.attributeSpecs),
            methodSpecs=",\n".join(self.methodSpecs),
            chromeOnlyAttributeSpecs=chromeOnlyAttributes[0],
            chromeOnlyMethodSpecs=chromeOnlyMethods[0],
            chromeOnlyAttributes=chromeOnlyAttributes[1],
            chromeOnlyMethods=chromeOnlyMethods[1],
        )


class CGCycleCollectionTraverseForOwningUnionMethod(CGAbstractMethod):
    """
    ImplCycleCollectionUnlink for owning union type.
    """

    def __init__(self, type):
        self.type = type
        args = [
            Argument("nsCycleCollectionTraversalCallback&", "aCallback"),
            Argument("%s&" % CGUnionStruct.unionTypeName(type, True), "aUnion"),
            Argument("const char*", "aName"),
            Argument("uint32_t", "aFlags", "0"),
        ]
        CGAbstractMethod.__init__(
            self, None, "ImplCycleCollectionTraverse", "void", args
        )

    def deps(self):
        return self.type.getDeps()

    def definition_body(self):
        memberNames = [
            getUnionMemberName(t)
            for t in self.type.flatMemberTypes
            if idlTypeNeedsCycleCollection(t)
        ]
        assert memberNames

        conditionTemplate = "aUnion.Is%s()"
        functionCallTemplate = (
            'ImplCycleCollectionTraverse(aCallback, aUnion.GetAs%s(), "m%s", aFlags);\n'
        )

        ifStaments = (
            CGIfWrapper(CGGeneric(functionCallTemplate % (m, m)), conditionTemplate % m)
            for m in memberNames
        )

        return CGElseChain(ifStaments).define()


class CGCycleCollectionUnlinkForOwningUnionMethod(CGAbstractMethod):
    """
    ImplCycleCollectionUnlink for owning union type.
    """

    def __init__(self, type):
        self.type = type
        args = [Argument("%s&" % CGUnionStruct.unionTypeName(type, True), "aUnion")]
        CGAbstractMethod.__init__(self, None, "ImplCycleCollectionUnlink", "void", args)

    def deps(self):
        return self.type.getDeps()

    def definition_body(self):
        return "aUnion.Uninit();\n"


builtinNames = {
    IDLType.Tags.bool: "bool",
    IDLType.Tags.int8: "int8_t",
    IDLType.Tags.int16: "int16_t",
    IDLType.Tags.int32: "int32_t",
    IDLType.Tags.int64: "int64_t",
    IDLType.Tags.uint8: "uint8_t",
    IDLType.Tags.uint16: "uint16_t",
    IDLType.Tags.uint32: "uint32_t",
    IDLType.Tags.uint64: "uint64_t",
    IDLType.Tags.unrestricted_float: "float",
    IDLType.Tags.float: "float",
    IDLType.Tags.unrestricted_double: "double",
    IDLType.Tags.double: "double",
}

numericSuffixes = {
    IDLType.Tags.int8: "",
    IDLType.Tags.uint8: "",
    IDLType.Tags.int16: "",
    IDLType.Tags.uint16: "",
    IDLType.Tags.int32: "",
    IDLType.Tags.uint32: "U",
    IDLType.Tags.int64: "LL",
    IDLType.Tags.uint64: "ULL",
    IDLType.Tags.unrestricted_float: "F",
    IDLType.Tags.float: "F",
    IDLType.Tags.unrestricted_double: "",
    IDLType.Tags.double: "",
}


def numericValue(t, v):
    if t == IDLType.Tags.unrestricted_double or t == IDLType.Tags.unrestricted_float:
        typeName = builtinNames[t]
        if v == float("inf"):
            return "mozilla::PositiveInfinity<%s>()" % typeName
        if v == float("-inf"):
            return "mozilla::NegativeInfinity<%s>()" % typeName
        if math.isnan(v):
            return "mozilla::UnspecifiedNaN<%s>()" % typeName
    return "%s%s" % (v, numericSuffixes[t])


class CastableObjectUnwrapper:
    """
    A class for unwrapping an object stored in a JS Value (or
    MutableHandle<Value> or Handle<Value>) named by the "source" and
    "mutableSource" arguments based on the passed-in descriptor and storing it
    in a variable called by the name in the "target" argument.  The "source"
    argument should be able to produce a Value or Handle<Value>; the
    "mutableSource" argument should be able to produce a MutableHandle<Value>

    codeOnFailure is the code to run if unwrapping fails.

    If isCallbackReturnValue is "JSImpl" and our descriptor is also
    JS-implemented, fall back to just creating the right object if what we
    have isn't one already.
    """

    def __init__(
        self,
        descriptor,
        source,
        mutableSource,
        target,
        codeOnFailure,
        exceptionCode=None,
        isCallbackReturnValue=False,
    ):
        self.substitution = {
            "type": descriptor.nativeType,
            "protoID": "prototypes::id::" + descriptor.name,
            "target": target,
            "codeOnFailure": codeOnFailure,
            "source": source,
            "mutableSource": mutableSource,
        }

        if isCallbackReturnValue == "JSImpl" and descriptor.interface.isJSImplemented():
            exceptionCode = exceptionCode or codeOnFailure
            self.substitution["codeOnFailure"] = fill(
                """
                // Be careful to not wrap random DOM objects here, even if
                // they're wrapped in opaque security wrappers for some reason.
                // XXXbz Wish we could check for a JS-implemented object
                // that already has a content reflection...
                if (!IsDOMObject(js::UncheckedUnwrap(&${source}.toObject()))) {
                  nsCOMPtr<nsIGlobalObject> contentGlobal;
                  JS::Rooted<JSObject*> callback(cx, CallbackOrNull());
                  if (!callback ||
                      !GetContentGlobalForJSImplementedObject(cx, callback, getter_AddRefs(contentGlobal))) {
                    $*{exceptionCode}
                  }
                  JS::Rooted<JSObject*> jsImplSourceObj(cx, &${source}.toObject());
                  MOZ_RELEASE_ASSERT(!js::IsWrapper(jsImplSourceObj),
                                     "Don't return JS implementations from other compartments");
                  JS::Rooted<JSObject*> jsImplSourceGlobal(cx, JS::GetNonCCWObjectGlobal(jsImplSourceObj));
                  ${target} = new ${type}(jsImplSourceObj, jsImplSourceGlobal, contentGlobal);
                } else {
                  $*{codeOnFailure}
                }
                """,
                exceptionCode=exceptionCode,
                **self.substitution,
            )
        else:
            self.substitution["codeOnFailure"] = codeOnFailure

    def __str__(self):
        substitution = self.substitution.copy()
        substitution["codeOnFailure"] %= {
            "securityError": "rv == NS_ERROR_XPC_SECURITY_MANAGER_VETO"
        }
        return fill(
            """
            {
              // Our JSContext should be in the right global to do unwrapping in.
              nsresult rv = UnwrapObject<${protoID}, ${type}>(${mutableSource}, ${target}, cx);
              if (NS_FAILED(rv)) {
                $*{codeOnFailure}
              }
            }
            """,
            **substitution,
        )


class FailureFatalCastableObjectUnwrapper(CastableObjectUnwrapper):
    """
    As CastableObjectUnwrapper, but defaulting to throwing if unwrapping fails
    """

    def __init__(
        self,
        descriptor,
        source,
        mutableSource,
        target,
        exceptionCode,
        isCallbackReturnValue,
        sourceDescription,
    ):
        CastableObjectUnwrapper.__init__(
            self,
            descriptor,
            source,
            mutableSource,
            target,
            'cx.ThrowErrorMessage<MSG_DOES_NOT_IMPLEMENT_INTERFACE>("%s", "%s");\n'
            "%s"
            % (sourceDescription, descriptor.interface.identifier.name, exceptionCode),
            exceptionCode,
            isCallbackReturnValue,
        )


def getCallbackConversionInfo(
    type, idlObject, isMember, isCallbackReturnValue, isOptional
):
    """
    Returns a tuple containing the declType, declArgs, and basic
    conversion for the given callback type, with the given callback
    idl object in the given context (isMember/isCallbackReturnValue/isOptional).
    """
    name = idlObject.identifier.name

    # We can't use fast callbacks if isOptional because then we get an
    # Optional<RootedCallback> thing, which is not transparent to consumers.
    useFastCallback = (
        (not isMember or isMember == "Union")
        and not isCallbackReturnValue
        and not isOptional
    )
    if useFastCallback:
        name = "binding_detail::Fast%s" % name
        rootArgs = ""
        args = "&${val}.toObject(), JS::CurrentGlobalOrNull(cx)"
    else:
        rootArgs = dedent(
            """
            JS::Rooted<JSObject*> tempRoot(cx, &${val}.toObject());
            JS::Rooted<JSObject*> tempGlobalRoot(cx, JS::CurrentGlobalOrNull(cx));
            """
        )
        args = "cx, tempRoot, tempGlobalRoot, GetIncumbentGlobal()"

    if type.nullable() or isCallbackReturnValue:
        declType = CGGeneric("RefPtr<%s>" % name)
    else:
        declType = CGGeneric("OwningNonNull<%s>" % name)

    if useFastCallback:
        declType = CGTemplatedType("RootedCallback", declType)
        declArgs = "cx"
    else:
        declArgs = None

    conversion = fill(
        """
        { // scope for tempRoot and tempGlobalRoot if needed
          $*{rootArgs}
          $${declName} = new ${name}(${args});
        }
        """,
        rootArgs=rootArgs,
        name=name,
        args=args,
    )
    return (declType, declArgs, conversion)


class JSToNativeConversionInfo:
    """
    An object representing information about a JS-to-native conversion.
    """

    def __init__(
        self,
        template,
        declType=None,
        holderType=None,
        dealWithOptional=False,
        declArgs=None,
        holderArgs=None,
    ):
        """
        template: A string representing the conversion code.  This will have
                  template substitution performed on it as follows:

          ${val} is a handle to the JS::Value in question
          ${maybeMutableVal} May be a mutable handle to the JS::Value in
                             question. This is only OK to use if ${val} is
                             known to not be undefined.
          ${holderName} replaced by the holder's name, if any
          ${declName} replaced by the declaration's name
          ${haveValue} replaced by an expression that evaluates to a boolean
                       for whether we have a JS::Value.  Only used when
                       defaultValue is not None or when True is passed for
                       checkForValue to instantiateJSToNativeConversion.
                       This expression may not be already-parenthesized, so if
                       you use it with && or || make sure to put parens
                       around it.
          ${passedToJSImpl} replaced by an expression that evaluates to a boolean
                            for whether this value is being passed to a JS-
                            implemented interface.

        declType: A CGThing representing the native C++ type we're converting
                  to.  This is allowed to be None if the conversion code is
                  supposed to be used as-is.

        holderType: A CGThing representing the type of a "holder" which will
                    hold a possible reference to the C++ thing whose type we
                    returned in declType, or  None if no such holder is needed.

        dealWithOptional: A boolean indicating whether the caller has to do
                          optional-argument handling.  This should only be set
                          to true if the JS-to-native conversion is being done
                          for an optional argument or dictionary member with no
                          default value and if the returned template expects
                          both declType and holderType to be wrapped in
                          Optional<>, with ${declName} and ${holderName}
                          adjusted to point to the Value() of the Optional, and
                          Construct() calls to be made on the Optional<>s as
                          needed.

        declArgs: If not None, the arguments to pass to the ${declName}
                  constructor.  These will have template substitution performed
                  on them so you can use things like ${val}.  This is a
                  single string, not a list of strings.

        holderArgs: If not None, the arguments to pass to the ${holderName}
                    constructor.  These will have template substitution
                    performed on them so you can use things like ${val}.
                    This is a single string, not a list of strings.

        ${declName} must be in scope before the code from 'template' is entered.

        If holderType is not None then ${holderName} must be in scope before
        the code from 'template' is entered.
        """
        assert isinstance(template, str)
        assert declType is None or isinstance(declType, CGThing)
        assert holderType is None or isinstance(holderType, CGThing)
        self.template = template
        self.declType = declType
        self.holderType = holderType
        self.dealWithOptional = dealWithOptional
        self.declArgs = declArgs
        self.holderArgs = holderArgs


def getHandleDefault(defaultValue):
    tag = defaultValue.type.tag()
    if tag in numericSuffixes:
        # Some numeric literals require a suffix to compile without warnings
        return numericValue(tag, defaultValue.value)
    assert tag == IDLType.Tags.bool
    return toStringBool(defaultValue.value)


def handleDefaultStringValue(defaultValue, method):
    """
    Returns a string which ends up calling 'method' with a (char_t*, length)
    pair that sets this string default value.  This string is suitable for
    passing as the second argument of handleDefault.
    """
    assert (
        defaultValue.type.isDOMString()
        or defaultValue.type.isUSVString()
        or defaultValue.type.isUTF8String()
        or defaultValue.type.isByteString()
    )
    # There shouldn't be any non-ASCII or embedded nulls in here; if
    # it ever sneaks in we will need to think about how to properly
    # represent that in the C++.
    assert all(ord(c) < 128 and ord(c) > 0 for c in defaultValue.value)
    if defaultValue.type.isByteString() or defaultValue.type.isUTF8String():
        prefix = ""
    else:
        prefix = "u"
    return fill(
        """
        ${method}(${prefix}"${value}");
        """,
        method=method,
        prefix=prefix,
        value=defaultValue.value,
    )


def recordKeyType(recordType):
    assert recordType.keyType.isString()
    if recordType.keyType.isByteString() or recordType.keyType.isUTF8String():
        return "nsCString"
    return "nsString"


def recordKeyDeclType(recordType):
    return CGGeneric(recordKeyType(recordType))


def initializerForType(type):
    """
    Get the right initializer for the given type for a data location where we
    plan to then initialize it from a JS::Value.  Some types need to always be
    initialized even before we start the JS::Value-to-IDL-value conversion.

    Returns a string or None if no initialization is needed.
    """
    if type.isObject():
        return "nullptr"
    # We could probably return CGDictionary.getNonInitializingCtorArg() for the
    # dictionary case, but code outside DictionaryBase subclasses can't use
    # that, so we can't do it across the board.
    return None


# If this function is modified, modify CGNativeMember.getArg and
# CGNativeMember.getRetvalInfo accordingly.  The latter cares about the decltype
# and holdertype we end up using, because it needs to be able to return the code
# that will convert those to the actual return value of the callback function.
def getJSToNativeConversionInfo(
    type,
    descriptorProvider,
    failureCode=None,
    isDefinitelyObject=False,
    isMember=False,
    isOptional=False,
    invalidEnumValueFatal=True,
    defaultValue=None,
    isNullOrUndefined=False,
    isKnownMissing=False,
    exceptionCode=None,
    lenientFloatCode=None,
    allowTreatNonCallableAsNull=False,
    isCallbackReturnValue=False,
    sourceDescription="value",
    nestingLevel="",
):
    """
    Get a template for converting a JS value to a native object based on the
    given type and descriptor.  If failureCode is given, then we're actually
    testing whether we can convert the argument to the desired type.  That
    means that failures to convert due to the JS value being the wrong type of
    value need to use failureCode instead of throwing exceptions.  Failures to
    convert that are due to JS exceptions (from toString or valueOf methods) or
    out of memory conditions need to throw exceptions no matter what
    failureCode is.  However what actually happens when throwing an exception
    can be controlled by exceptionCode.  The only requirement on that is that
    exceptionCode must end up doing a return, and every return from this
    function must happen via exceptionCode if exceptionCode is not None.

    If isDefinitelyObject is True, that means we have a value and the value
    tests true for isObject(), so we have no need to recheck that.

    If isNullOrUndefined is True, that means we have a value and the value
    tests true for isNullOrUndefined(), so we have no need to recheck that.

    If isKnownMissing is True, that means that we are known-missing, and for
    cases when we have a default value we only need to output the default value.

    if isMember is not False, we're being converted from a property of some JS
    object, not from an actual method argument, so we can't rely on our jsval
    being rooted or outliving us in any way.  Callers can pass "Dictionary",
    "Variadic", "Sequence", "Union", or "OwningUnion" to indicate that the conversion
    is for something that is a dictionary member, a variadic argument, a sequence,
    an union, or an owning union respectively.
    XXX Once we swtich *Rooter to Rooted* for Record and Sequence type entirely,
        we could remove "Union" from isMember.

    If isOptional is true, then we are doing conversion of an optional
    argument with no default value.

    invalidEnumValueFatal controls whether an invalid enum value conversion
    attempt will throw (if true) or simply return without doing anything (if
    false).

    If defaultValue is not None, it's the IDL default value for this conversion

    If isEnforceRange is true, we're converting an integer and throwing if the
    value is out of range.

    If isClamp is true, we're converting an integer and clamping if the
    value is out of range.

    If isAllowShared is false, we're converting a buffer source and throwing if
    it is a SharedArrayBuffer or backed by a SharedArrayBuffer.

    If lenientFloatCode is not None, it should be used in cases when
    we're a non-finite float that's not unrestricted.

    If allowTreatNonCallableAsNull is true, then [TreatNonCallableAsNull] and
    [LegacyTreatNonObjectAsNull] extended attributes on nullable callback functions
    will be honored.

    If isCallbackReturnValue is "JSImpl" or "Callback", then the declType may be
    adjusted to make it easier to return from a callback.  Since that type is
    never directly observable by any consumers of the callback code, this is OK.
    Furthermore, if isCallbackReturnValue is "JSImpl", that affects the behavior
    of the FailureFatalCastableObjectUnwrapper conversion; this is used for
    implementing auto-wrapping of JS-implemented return values from a
    JS-implemented interface.

    sourceDescription is a description of what this JS value represents, to be
    used in error reporting.  Callers should assume that it might get placed in
    the middle of a sentence.  If it ends up at the beginning of a sentence, its
    first character will be automatically uppercased.

    The return value from this function is a JSToNativeConversionInfo.
    """
    # If we have a defaultValue then we're not actually optional for
    # purposes of what we need to be declared as.
    assert defaultValue is None or not isOptional

    # Also, we should not have a defaultValue if we know we're an object
    assert not isDefinitelyObject or defaultValue is None

    # And we can't both be an object and be null or undefined
    assert not isDefinitelyObject or not isNullOrUndefined

    isClamp = type.hasClamp()
    isEnforceRange = type.hasEnforceRange()
    isAllowShared = type.hasAllowShared()

    # If exceptionCode is not set, we'll just rethrow the exception we got.
    # Note that we can't just set failureCode to exceptionCode, because setting
    # failureCode will prevent pending exceptions from being set in cases when
    # they really should be!
    if exceptionCode is None:
        exceptionCode = "return false;\n"

    # Unfortunately, .capitalize() on a string will lowercase things inside the
    # string, which we do not want.
    def firstCap(string):
        return string[0].upper() + string[1:]

    # Helper functions for dealing with failures due to the JS value being the
    # wrong type of value
    def onFailureNotAnObject(failureCode):
        return CGGeneric(
            failureCode
            or (
                'cx.ThrowErrorMessage<MSG_NOT_OBJECT>("%s");\n'
                "%s" % (firstCap(sourceDescription), exceptionCode)
            )
        )

    def onFailureBadType(failureCode, typeName):
        return CGGeneric(
            failureCode
            or (
                'cx.ThrowErrorMessage<MSG_DOES_NOT_IMPLEMENT_INTERFACE>("%s", "%s");\n'
                "%s" % (firstCap(sourceDescription), typeName, exceptionCode)
            )
        )

    # It's a failure in the committed-to conversion, not a failure to match up
    # to a type, so we don't want to use failureCode in here. We want to just
    # throw an exception unconditionally.
    def onFailureIsShared():
        return CGGeneric(
            'cx.ThrowErrorMessage<MSG_TYPEDARRAY_IS_SHARED>("%s");\n'
            "%s" % (firstCap(sourceDescription), exceptionCode)
        )

    def onFailureIsLarge():
        return CGGeneric(
            'cx.ThrowErrorMessage<MSG_TYPEDARRAY_IS_LARGE>("%s");\n'
            "%s" % (firstCap(sourceDescription), exceptionCode)
        )

    def onFailureIsResizable():
        return CGGeneric(
            'cx.ThrowErrorMessage<MSG_TYPEDARRAY_IS_RESIZABLE>("%s");\n'
            "%s" % (firstCap(sourceDescription), exceptionCode)
        )

    def onFailureNotCallable(failureCode):
        return CGGeneric(
            failureCode
            or (
                'cx.ThrowErrorMessage<MSG_NOT_CALLABLE>("%s");\n'
                "%s" % (firstCap(sourceDescription), exceptionCode)
            )
        )

    # A helper function for handling default values.  Takes a template
    # body and the C++ code to set the default value and wraps the
    # given template body in handling for the default value.
    def handleDefault(template, setDefault):
        if defaultValue is None:
            return template
        if isKnownMissing:
            return fill(
                """
                {
                  // scope for any temporaries our default value setting needs.
                  $*{setDefault}
                }
                """,
                setDefault=setDefault,
            )
        return fill(
            """
            if ($${haveValue}) {
              $*{templateBody}
            } else {
              $*{setDefault}
            }
            """,
            templateBody=template,
            setDefault=setDefault,
        )

    # A helper function for wrapping up the template body for
    # possibly-nullable objecty stuff
    def wrapObjectTemplate(templateBody, type, codeToSetNull, failureCode=None):
        if isNullOrUndefined and type.nullable():
            # Just ignore templateBody and set ourselves to null.
            # Note that we don't have to worry about default values
            # here either, since we already examined this value.
            return codeToSetNull

        if not isDefinitelyObject:
            # Handle the non-object cases by wrapping up the whole
            # thing in an if cascade.
            if type.nullable():
                elifLine = "} else if (${val}.isNullOrUndefined()) {\n"
                elifBody = codeToSetNull
            else:
                elifLine = ""
                elifBody = ""

            # Note that $${val} below expands to ${val}. This string is
            # used as a template later, and val will be filled in then.
            templateBody = fill(
                """
                if ($${val}.isObject()) {
                  $*{templateBody}
                $*{elifLine}
                  $*{elifBody}
                } else {
                  $*{failureBody}
                }
                """,
                templateBody=templateBody,
                elifLine=elifLine,
                elifBody=elifBody,
                failureBody=onFailureNotAnObject(failureCode).define(),
            )

            if isinstance(defaultValue, IDLNullValue):
                assert type.nullable()  # Parser should enforce this
                templateBody = handleDefault(templateBody, codeToSetNull)
            elif isinstance(defaultValue, IDLEmptySequenceValue):
                # Our caller will handle it
                pass
            else:
                assert defaultValue is None

        return templateBody

    # A helper function for converting things that look like a JSObject*.
    def handleJSObjectType(
        type, isMember, failureCode, exceptionCode, sourceDescription
    ):
        if not isMember or isMember == "Union":
            if isOptional:
                # We have a specialization of Optional that will use a
                # Rooted for the storage here.
                declType = CGGeneric("JS::Handle<JSObject*>")
            else:
                declType = CGGeneric("JS::Rooted<JSObject*>")
            declArgs = "cx"
        else:
            assert isMember in (
                "Sequence",
                "Variadic",
                "Dictionary",
                "OwningUnion",
                "Record",
            )
            # We'll get traced by the sequence or dictionary or union tracer
            declType = CGGeneric("JSObject*")
            declArgs = None
        templateBody = "${declName} = &${val}.toObject();\n"

        # For JS-implemented APIs, we refuse to allow passing objects that the
        # API consumer does not subsume. The extra parens around
        # ($${passedToJSImpl}) suppress unreachable code warnings when
        # $${passedToJSImpl} is the literal `false`.  But Apple is shipping a
        # buggy clang (clang 3.9) in Xcode 8.3, so there even the parens are not
        # enough.  So we manually disable some warnings in clang.
        if (
            not isinstance(descriptorProvider, Descriptor)
            or descriptorProvider.interface.isJSImplemented()
        ):
            templateBody = (
                fill(
                    """
                #ifdef __clang__
                #pragma clang diagnostic push
                #pragma clang diagnostic ignored "-Wunreachable-code"
                #pragma clang diagnostic ignored "-Wunreachable-code-return"
                #endif // __clang__
                if (($${passedToJSImpl}) && !CallerSubsumes($${val})) {
                  cx.ThrowErrorMessage<MSG_PERMISSION_DENIED_TO_PASS_ARG>("${sourceDescription}");
                  $*{exceptionCode}
                }
                #ifdef __clang__
                #pragma clang diagnostic pop
                #endif // __clang__
                """,
                    sourceDescription=sourceDescription,
                    exceptionCode=exceptionCode,
                )
                + templateBody
            )

        setToNullCode = "${declName} = nullptr;\n"
        template = wrapObjectTemplate(templateBody, type, setToNullCode, failureCode)
        return JSToNativeConversionInfo(
            template, declType=declType, dealWithOptional=isOptional, declArgs=declArgs
        )

    def incrementNestingLevel():
        if nestingLevel == "":
            return 1
        return nestingLevel + 1

    assert not (isEnforceRange and isClamp)  # These are mutually exclusive

    if type.isSequence() or type.isObservableArray():
        assert not isEnforceRange and not isClamp and not isAllowShared

        if failureCode is None:
            notSequence = (
                'cx.ThrowErrorMessage<MSG_CONVERSION_ERROR>("%s", "%s");\n'
                "%s"
                % (
                    firstCap(sourceDescription),
                    "sequence" if type.isSequence() else "observable array",
                    exceptionCode,
                )
            )
        else:
            notSequence = failureCode

        nullable = type.nullable()
        # Be very careful not to change "type": we need it later
        if nullable:
            elementType = type.inner.inner
        else:
            elementType = type.inner

        # We want to use auto arrays if we can, but we have to be careful with
        # reallocation behavior for arrays.  In particular, if we use auto
        # arrays for sequences and have a sequence of elements which are
        # themselves sequences or have sequences as members, we have a problem.
        # In that case, resizing the outermost AutoTArray to the right size
        # will memmove its elements, but AutoTArrays are not memmovable and
        # hence will end up with pointers to bogus memory, which is bad.  To
        # deal with this, we typically map WebIDL sequences to our Sequence
        # type, which is in fact memmovable.  The one exception is when we're
        # passing in a sequence directly as an argument without any sort of
        # optional or nullable complexity going on.  In that situation, we can
        # use an AutoSequence instead.  We have to keep using Sequence in the
        # nullable and optional cases because we don't want to leak the
        # AutoSequence type to consumers, which would be unavoidable with
        # Nullable<AutoSequence> or Optional<AutoSequence>.
        if (
            (isMember and isMember != "Union")
            or isOptional
            or nullable
            or isCallbackReturnValue
        ):
            sequenceClass = "Sequence"
        else:
            sequenceClass = "binding_detail::AutoSequence"

        # XXXbz we can't include the index in the sourceDescription, because
        # we don't really have a way to pass one in dynamically at runtime...
        elementInfo = getJSToNativeConversionInfo(
            elementType,
            descriptorProvider,
            isMember="Sequence",
            exceptionCode=exceptionCode,
            lenientFloatCode=lenientFloatCode,
            isCallbackReturnValue=isCallbackReturnValue,
            sourceDescription="element of %s" % sourceDescription,
            nestingLevel=incrementNestingLevel(),
        )
        if elementInfo.dealWithOptional:
            raise TypeError("Shouldn't have optional things in sequences")
        if elementInfo.holderType is not None:
            raise TypeError("Shouldn't need holders for sequences")

        typeName = CGTemplatedType(sequenceClass, elementInfo.declType)
        sequenceType = typeName.define()

        if isMember == "Union" and typeNeedsRooting(type):
            assert not nullable
            typeName = CGTemplatedType(
                "binding_detail::RootedAutoSequence", elementInfo.declType
            )
        elif nullable:
            typeName = CGTemplatedType("Nullable", typeName)

        if nullable:
            arrayRef = "${declName}.SetValue()"
        else:
            arrayRef = "${declName}"

        elementConversion = string.Template(elementInfo.template).substitute(
            {
                "val": "temp" + str(nestingLevel),
                "maybeMutableVal": "&temp" + str(nestingLevel),
                "declName": "slot" + str(nestingLevel),
                # We only need holderName here to handle isExternal()
                # interfaces, which use an internal holder for the
                # conversion even when forceOwningType ends up true.
                "holderName": "tempHolder" + str(nestingLevel),
                "passedToJSImpl": "${passedToJSImpl}",
            }
        )

        elementInitializer = initializerForType(elementType)
        if elementInitializer is None:
            elementInitializer = ""
        else:
            elementInitializer = elementInitializer + ", "

        # NOTE: Keep this in sync with variadic conversions as needed
        templateBody = fill(
            """
            JS::ForOfIterator iter${nestingLevel}(cx);
            if (!iter${nestingLevel}.init($${val}, JS::ForOfIterator::AllowNonIterable)) {
              $*{exceptionCode}
            }
            if (!iter${nestingLevel}.valueIsIterable()) {
              $*{notSequence}
            }
            ${sequenceType} &arr${nestingLevel} = ${arrayRef};
            JS::Rooted<JS::Value> temp${nestingLevel}(cx);
            while (true) {
              bool done${nestingLevel};
              if (!iter${nestingLevel}.next(&temp${nestingLevel}, &done${nestingLevel})) {
                $*{exceptionCode}
              }
              if (done${nestingLevel}) {
                break;
              }
              ${elementType}* slotPtr${nestingLevel} = arr${nestingLevel}.AppendElement(${elementInitializer}mozilla::fallible);
              if (!slotPtr${nestingLevel}) {
                JS_ReportOutOfMemory(cx);
                $*{exceptionCode}
              }
              ${elementType}& slot${nestingLevel} = *slotPtr${nestingLevel};
              $*{elementConversion}
            }
            """,
            exceptionCode=exceptionCode,
            notSequence=notSequence,
            sequenceType=sequenceType,
            arrayRef=arrayRef,
            elementType=elementInfo.declType.define(),
            elementConversion=elementConversion,
            elementInitializer=elementInitializer,
            nestingLevel=str(nestingLevel),
        )

        templateBody = wrapObjectTemplate(
            templateBody, type, "${declName}.SetNull();\n", notSequence
        )
        if isinstance(defaultValue, IDLEmptySequenceValue):
            if type.nullable():
                codeToSetEmpty = "${declName}.SetValue();\n"
            else:
                codeToSetEmpty = (
                    "/* ${declName} array is already empty; nothing to do */\n"
                )
            templateBody = handleDefault(templateBody, codeToSetEmpty)

        declArgs = None
        holderType = None
        holderArgs = None
        # Sequence arguments that might contain traceable things need
        # to get traced
        if typeNeedsRooting(elementType):
            if not isMember:
                holderType = CGTemplatedType("SequenceRooter", elementInfo.declType)
                # If our sequence is nullable, this will set the Nullable to be
                # not-null, but that's ok because we make an explicit SetNull() call
                # on it as needed if our JS value is actually null.
                holderArgs = "cx, &%s" % arrayRef
            elif isMember == "Union":
                declArgs = "cx"

        return JSToNativeConversionInfo(
            templateBody,
            declType=typeName,
            declArgs=declArgs,
            holderType=holderType,
            dealWithOptional=isOptional,
            holderArgs=holderArgs,
        )

    if type.isRecord():
        assert not isEnforceRange and not isClamp and not isAllowShared
        if failureCode is None:
            notRecord = 'cx.ThrowErrorMessage<MSG_NOT_OBJECT>("%s");\n' "%s" % (
                firstCap(sourceDescription),
                exceptionCode,
            )
        else:
            notRecord = failureCode

        nullable = type.nullable()
        # Be very careful not to change "type": we need it later
        if nullable:
            recordType = type.inner
        else:
            recordType = type
        valueType = recordType.inner

        valueInfo = getJSToNativeConversionInfo(
            valueType,
            descriptorProvider,
            isMember="Record",
            exceptionCode=exceptionCode,
            lenientFloatCode=lenientFloatCode,
            isCallbackReturnValue=isCallbackReturnValue,
            sourceDescription="value in %s" % sourceDescription,
            nestingLevel=incrementNestingLevel(),
        )
        if valueInfo.dealWithOptional:
            raise TypeError("Shouldn't have optional things in record")
        if valueInfo.holderType is not None:
            raise TypeError("Shouldn't need holders for record")

        declType = CGTemplatedType(
            "Record", [recordKeyDeclType(recordType), valueInfo.declType]
        )
        typeName = declType.define()

        if isMember == "Union" and typeNeedsRooting(type):
            assert not nullable
            declType = CGTemplatedType(
                "RootedRecord", [recordKeyDeclType(recordType), valueInfo.declType]
            )
        elif nullable:
            declType = CGTemplatedType("Nullable", declType)

        if nullable:
            recordRef = "${declName}.SetValue()"
        else:
            recordRef = "${declName}"

        valueConversion = string.Template(valueInfo.template).substitute(
            {
                "val": "temp",
                "maybeMutableVal": "&temp",
                "declName": "slot",
                # We only need holderName here to handle isExternal()
                # interfaces, which use an internal holder for the
                # conversion even when forceOwningType ends up true.
                "holderName": "tempHolder",
                "passedToJSImpl": "${passedToJSImpl}",
            }
        )

        keyType = recordKeyType(recordType)
        if recordType.keyType.isJSString():
            raise TypeError(
                "Have do deal with JSString record type, but don't know how"
            )
        if recordType.keyType.isByteString() or recordType.keyType.isUTF8String():
            hashKeyType = "nsCStringHashKey"
            if recordType.keyType.isByteString():
                keyConversionFunction = "ConvertJSValueToByteString"
            else:
                keyConversionFunction = "ConvertJSValueToString"

        else:
            hashKeyType = "nsStringHashKey"
            if recordType.keyType.isDOMString():
                keyConversionFunction = "ConvertJSValueToString"
            else:
                assert recordType.keyType.isUSVString()
                keyConversionFunction = "ConvertJSValueToUSVString"

        templateBody = fill(
            """
            auto& recordEntries = ${recordRef}.Entries();

            JS::Rooted<JSObject*> recordObj(cx, &$${val}.toObject());
            JS::RootedVector<jsid> ids(cx);
            if (!js::GetPropertyKeys(cx, recordObj,
                                     JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS, &ids)) {
              $*{exceptionCode}
            }
            if (!recordEntries.SetCapacity(ids.length(), mozilla::fallible)) {
              JS_ReportOutOfMemory(cx);
              $*{exceptionCode}
            }
            JS::Rooted<JS::Value> propNameValue(cx);
            JS::Rooted<JS::Value> temp(cx);
            JS::Rooted<jsid> curId(cx);
            JS::Rooted<JS::Value> idVal(cx);
            // Use a hashset to keep track of ids seen, to avoid
            // introducing nasty O(N^2) behavior scanning for them all the
            // time.  Ideally we'd use a data structure with O(1) lookup
            // _and_ ordering for the MozMap, but we don't have one lying
            // around.
            nsTHashtable<${hashKeyType}> idsSeen;
            for (size_t i = 0; i < ids.length(); ++i) {
              curId = ids[i];

              JS::Rooted<mozilla::Maybe<JS::PropertyDescriptor>> desc(cx);
              if (!JS_GetOwnPropertyDescriptorById(cx, recordObj, curId,
                                                   &desc)) {
                $*{exceptionCode}
              }

              if (desc.isNothing() || !desc->enumerable()) {
                continue;
              }

              idVal = js::IdToValue(curId);
              ${keyType} propName;
              // This will just throw if idVal is a Symbol, like the spec says
              // to do.
              if (!${keyConversionFunction}(cx, idVal, "key of ${sourceDescription}", propName)) {
                $*{exceptionCode}
              }

              if (!JS_GetPropertyById(cx, recordObj, curId, &temp)) {
                $*{exceptionCode}
              }

              ${typeName}::EntryType* entry;
              if (!idsSeen.EnsureInserted(propName)) {
                // Find the existing entry.
                auto idx = recordEntries.IndexOf(propName);
                MOZ_ASSERT(idx != recordEntries.NoIndex,
                           "Why is it not found?");
                // Now blow it away to make it look like it was just added
                // to the array, because it's not obvious that it's
                // safe to write to its already-initialized mValue via our
                // normal codegen conversions.  For example, the value
                // could be a union and this would change its type, but
                // codegen assumes we won't do that.
                entry = recordEntries.ReconstructElementAt(idx);
              } else {
                // Safe to do an infallible append here, because we did a
                // SetCapacity above to the right capacity.
                entry = recordEntries.AppendElement();
              }
              entry->mKey = propName;
              ${valueType}& slot = entry->mValue;
              $*{valueConversion}
            }
            """,
            exceptionCode=exceptionCode,
            recordRef=recordRef,
            hashKeyType=hashKeyType,
            keyType=keyType,
            keyConversionFunction=keyConversionFunction,
            sourceDescription=sourceDescription,
            typeName=typeName,
            valueType=valueInfo.declType.define(),
            valueConversion=valueConversion,
        )

        templateBody = wrapObjectTemplate(
            templateBody, type, "${declName}.SetNull();\n", notRecord
        )

        declArgs = None
        holderType = None
        holderArgs = None
        # record arguments that might contain traceable things need
        # to get traced
        if not isMember and isCallbackReturnValue:
            # Go ahead and just convert directly into our actual return value
            declType = CGWrapper(declType, post="&")
            declArgs = "aRetVal"
        elif typeNeedsRooting(valueType):
            if not isMember:
                holderType = CGTemplatedType(
                    "RecordRooter", [recordKeyDeclType(recordType), valueInfo.declType]
                )
                # If our record is nullable, this will set the Nullable to be
                # not-null, but that's ok because we make an explicit SetNull() call
                # on it as needed if our JS value is actually null.
                holderArgs = "cx, &%s" % recordRef
            elif isMember == "Union":
                declArgs = "cx"

        return JSToNativeConversionInfo(
            templateBody,
            declType=declType,
            declArgs=declArgs,
            holderType=holderType,
            dealWithOptional=isOptional,
            holderArgs=holderArgs,
        )

    if type.isUnion():
        nullable = type.nullable()
        if nullable:
            type = type.inner

        isOwningUnion = (isMember and isMember != "Union") or isCallbackReturnValue
        unionArgumentObj = "${declName}"
        if nullable:
            if isOptional and not isOwningUnion:
                unionArgumentObj += ".Value()"
            # If we're owning, we're a Nullable, which hasn't been told it has
            # a value.  Otherwise we're an already-constructed Maybe.
            unionArgumentObj += ".SetValue()"

        templateBody = CGIfWrapper(
            CGGeneric(exceptionCode),
            '!%s.Init(cx, ${val}, "%s", ${passedToJSImpl})'
            % (unionArgumentObj, firstCap(sourceDescription)),
        )

        if type.hasNullableType:
            assert not nullable
            # Make sure to handle a null default value here
            if defaultValue and isinstance(defaultValue, IDLNullValue):
                assert defaultValue.type == type
                templateBody = CGIfElseWrapper(
                    "!(${haveValue})",
                    CGGeneric("%s.SetNull();\n" % unionArgumentObj),
                    templateBody,
                )

        typeName = CGUnionStruct.unionTypeDecl(type, isOwningUnion)
        argumentTypeName = typeName + "Argument"
        if nullable:
            typeName = "Nullable<" + typeName + " >"

        declType = CGGeneric(typeName)
        if isOwningUnion:
            holderType = None
        else:
            holderType = CGGeneric(argumentTypeName)
            if nullable:
                holderType = CGTemplatedType("Maybe", holderType)

        # If we're isOptional and not nullable the normal optional handling will
        # handle lazy construction of our holder.  If we're nullable and not
        # owning we do it all by hand because we do not want our holder
        # constructed if we're null.  But if we're owning we don't have a
        # holder anyway, so we can do the normal Optional codepath.
        declLoc = "${declName}"
        constructDecl = None
        if nullable:
            if isOptional and not isOwningUnion:
                declType = CGTemplatedType("Optional", declType)
                constructDecl = CGGeneric("${declName}.Construct();\n")
                declLoc = "${declName}.Value()"

        if not isMember and isCallbackReturnValue:
            declType = CGWrapper(declType, post="&")
            declArgs = "aRetVal"
        else:
            declArgs = None

        if (
            defaultValue
            and not isinstance(defaultValue, IDLNullValue)
            and not isinstance(defaultValue, IDLDefaultDictionaryValue)
        ):
            tag = defaultValue.type.tag()

            if tag in numericSuffixes or tag is IDLType.Tags.bool:
                defaultStr = getHandleDefault(defaultValue)
                # Make sure we actually construct the thing inside the nullable.
                value = declLoc + (".SetValue()" if nullable else "")
                name = getUnionMemberName(defaultValue.type)
                default = CGGeneric(
                    "%s.RawSetAs%s() = %s;\n" % (value, name, defaultStr)
                )
            elif isinstance(defaultValue, IDLEmptySequenceValue):
                name = getUnionMemberName(defaultValue.type)
                # Make sure we actually construct the thing inside the nullable.
                value = declLoc + (".SetValue()" if nullable else "")
                if not isOwningUnion and typeNeedsRooting(defaultValue.type):
                    ctorArgs = "cx"
                else:
                    ctorArgs = ""
                # It's enough to set us to the right type; that will
                # create an empty array, which is all we need here.
                default = CGGeneric(
                    "Unused << %s.RawSetAs%s(%s);\n" % (value, name, ctorArgs)
                )
            elif defaultValue.type.isEnum():
                name = getUnionMemberName(defaultValue.type)
                # Make sure we actually construct the thing inside the nullable.
                value = declLoc + (".SetValue()" if nullable else "")
                default = CGGeneric(
                    "%s.RawSetAs%s() = %s::%s;\n"
                    % (
                        value,
                        name,
                        defaultValue.type.inner.identifier.name,
                        getEnumValueName(defaultValue.value),
                    )
                )
            else:
                default = CGGeneric(
                    handleDefaultStringValue(
                        defaultValue, "%s.SetStringLiteral" % unionArgumentObj
                    )
                )

            templateBody = CGIfElseWrapper("!(${haveValue})", default, templateBody)

        if nullable:
            assert not type.hasNullableType
            if defaultValue:
                if isinstance(defaultValue, IDLNullValue):
                    extraConditionForNull = "!(${haveValue}) || "
                else:
                    extraConditionForNull = "(${haveValue}) && "
            else:
                extraConditionForNull = ""

            hasUndefinedType = any(t.isUndefined() for t in type.flatMemberTypes)
            assert not hasUndefinedType or defaultValue is None

            nullTest = (
                "${val}.isNull()" if hasUndefinedType else "${val}.isNullOrUndefined()"
            )
            templateBody = CGIfElseWrapper(
                extraConditionForNull + nullTest,
                CGGeneric("%s.SetNull();\n" % declLoc),
                templateBody,
            )
        elif (
            not type.hasNullableType
            and defaultValue
            and isinstance(defaultValue, IDLDefaultDictionaryValue)
        ):
            assert type.hasDictionaryType()
            assert defaultValue.type.isDictionary()
            if not isOwningUnion and typeNeedsRooting(defaultValue.type):
                ctorArgs = "cx"
            else:
                ctorArgs = ""
            initDictionaryWithNull = CGIfWrapper(
                CGGeneric("return false;\n"),
                (
                    '!%s.RawSetAs%s(%s).Init(cx, JS::NullHandleValue, "Member of %s")'
                    % (
                        declLoc,
                        getUnionMemberName(defaultValue.type),
                        ctorArgs,
                        type.prettyName(),
                    )
                ),
            )
            templateBody = CGIfElseWrapper(
                "!(${haveValue})", initDictionaryWithNull, templateBody
            )

        templateBody = CGList([constructDecl, templateBody])

        return JSToNativeConversionInfo(
            templateBody.define(),
            declType=declType,
            declArgs=declArgs,
            dealWithOptional=isOptional and (not nullable or isOwningUnion),
        )

    if type.isPromise():
        assert not type.nullable()
        assert defaultValue is None

        # We always have to hold a strong ref to Promise here, because
        # Promise::resolve returns an addrefed thing.
        argIsPointer = isCallbackReturnValue
        if argIsPointer:
            declType = CGGeneric("RefPtr<Promise>")
        else:
            declType = CGGeneric("OwningNonNull<Promise>")

        # Per spec, what we're supposed to do is take the original
        # Promise.resolve and call it with the original Promise as this
        # value to make a Promise out of whatever value we actually have
        # here.  The question is which global we should use.  There are
        # several cases to consider:
        #
        # 1) Normal call to API with a Promise argument.  This is a case the
        #    spec covers, and we should be using the current Realm's
        #    Promise.  That means the current compartment.
        # 2) Call to API with a Promise argument over Xrays.  In practice,
        #    this sort of thing seems to be used for giving an API
        #    implementation a way to wait for conclusion of an asyc
        #    operation, _not_ to expose the Promise to content code.  So we
        #    probably want to allow callers to use such an API in a
        #    "natural" way, by passing chrome-side promises; indeed, that
        #    may be all that the caller has to represent their async
        #    operation.  That means we really need to do the
        #    Promise.resolve() in the caller (chrome) compartment: if we do
        #    it in the content compartment, we will try to call .then() on
        #    the chrome promise while in the content compartment, which will
        #    throw and we'll just get a rejected Promise.  Note that this is
        #    also the reason why a caller who has a chrome Promise
        #    representing an async operation can't itself convert it to a
        #    content-side Promise (at least not without some serious
        #    gyrations).
        # 3) Promise return value from a callback or callback interface.
        #    Per spec, this should use the Realm of the callback object.  In
        #    our case, that's the compartment of the underlying callback,
        #    not the current compartment (which may be the compartment of
        #    some cross-compartment wrapper around said callback).
        # 4) Return value from a JS-implemented interface.  In this case we
        #    have a problem.  Our current compartment is the compartment of
        #    the JS implementation.  But if the JS implementation returned
        #    a page-side Promise (which is a totally sane thing to do, and
        #    in fact the right thing to do given that this return value is
        #    going right to content script) then we don't want to
        #    Promise.resolve with our current compartment Promise, because
        #    that will wrap it up in a chrome-side Promise, which is
        #    decidedly _not_ what's desired here.  So in that case we
        #    should really unwrap the return value and use the global of
        #    the result.  CheckedUnwrapStatic should be good enough for that;
        #    if it fails, then we're failing unwrap while in a
        #    system-privileged compartment, so presumably we have a dead
        #    object wrapper.  Just error out.  Do NOT fall back to using
        #    the current compartment instead: that will return a
        #    system-privileged rejected (because getting .then inside
        #    resolve() failed) Promise to the caller, which they won't be
        #    able to touch.  That's not helpful.  If we error out, on the
        #    other hand, they will get a content-side rejected promise.
        #    Same thing if the value returned is not even an object.
        if isCallbackReturnValue == "JSImpl":
            # Case 4 above.  Note that globalObj defaults to the current
            # compartment global.  Note that we don't use $*{exceptionCode}
            # here because that will try to aRv.Throw(NS_ERROR_UNEXPECTED)
            # which we don't really want here.
            assert exceptionCode == "aRv.Throw(NS_ERROR_UNEXPECTED);\nreturn nullptr;\n"
            getPromiseGlobal = fill(
                """
                if (!$${val}.isObject()) {
                  aRv.ThrowTypeError<MSG_NOT_OBJECT>("${sourceDescription}");
                  return nullptr;
                }
                JSObject* unwrappedVal = js::CheckedUnwrapStatic(&$${val}.toObject());
                if (!unwrappedVal) {
                  // A slight lie, but not much of one, for a dead object wrapper.
                  aRv.ThrowTypeError<MSG_NOT_OBJECT>("${sourceDescription}");
                  return nullptr;
                }
                globalObj = JS::GetNonCCWObjectGlobal(unwrappedVal);
                """,
                sourceDescription=sourceDescription,
            )
        elif isCallbackReturnValue == "Callback":
            getPromiseGlobal = dedent(
                """
                // We basically want our entry global here.  Play it safe
                // and use GetEntryGlobal() to get it, with whatever
                // principal-clamping it ends up doing.
                globalObj = GetEntryGlobal()->GetGlobalJSObject();
                """
            )
        else:
            getPromiseGlobal = dedent(
                """
                globalObj = JS::CurrentGlobalOrNull(cx);
                """
            )

        templateBody = fill(
            """
            { // Scope for our GlobalObject, FastErrorResult, JSAutoRealm,
              // etc.

              JS::Rooted<JSObject*> globalObj(cx);
              $*{getPromiseGlobal}
              JSAutoRealm ar(cx, globalObj);
              GlobalObject promiseGlobal(cx, globalObj);
              if (promiseGlobal.Failed()) {
                $*{exceptionCode}
              }

              JS::Rooted<JS::Value> valueToResolve(cx, $${val});
              if (!JS_WrapValue(cx, &valueToResolve)) {
                $*{exceptionCode}
              }
              binding_detail::FastErrorResult promiseRv;
              nsCOMPtr<nsIGlobalObject> global =
                do_QueryInterface(promiseGlobal.GetAsSupports());
              if (!global) {
                promiseRv.Throw(NS_ERROR_UNEXPECTED);
                MOZ_ALWAYS_TRUE(promiseRv.MaybeSetPendingException(cx));
                $*{exceptionCode}
              }
              $${declName} = Promise::Resolve(global, cx, valueToResolve,
                                              promiseRv);
              if (promiseRv.MaybeSetPendingException(cx)) {
                $*{exceptionCode}
              }
            }
            """,
            getPromiseGlobal=getPromiseGlobal,
            exceptionCode=exceptionCode,
        )

        return JSToNativeConversionInfo(
            templateBody, declType=declType, dealWithOptional=isOptional
        )

    if type.isGeckoInterface():
        assert not isEnforceRange and not isClamp and not isAllowShared

        descriptor = descriptorProvider.getDescriptor(
            type.unroll().inner.identifier.name
        )

        assert descriptor.nativeType != "JSObject"

        if descriptor.interface.isCallback():
            (declType, declArgs, conversion) = getCallbackConversionInfo(
                type, descriptor.interface, isMember, isCallbackReturnValue, isOptional
            )
            template = wrapObjectTemplate(
                conversion, type, "${declName} = nullptr;\n", failureCode
            )
            return JSToNativeConversionInfo(
                template,
                declType=declType,
                declArgs=declArgs,
                dealWithOptional=isOptional,
            )

        if descriptor.interface.identifier.name == "WindowProxy":
            declType = CGGeneric("mozilla::dom::WindowProxyHolder")
            if type.nullable():
                declType = CGTemplatedType("Nullable", declType)
                windowProxyHolderRef = "${declName}.SetValue()"
            else:
                windowProxyHolderRef = "${declName}"

            failureCode = onFailureBadType(
                failureCode, descriptor.interface.identifier.name
            ).define()
            templateBody = fill(
                """
                JS::Rooted<JSObject*> source(cx, &$${val}.toObject());
                if (NS_FAILED(UnwrapWindowProxyArg(cx, source, ${windowProxyHolderRef}))) {
                    $*{onFailure}
                }
                """,
                windowProxyHolderRef=windowProxyHolderRef,
                onFailure=failureCode,
            )
            templateBody = wrapObjectTemplate(
                templateBody, type, "${declName}.SetNull();\n", failureCode
            )
            return JSToNativeConversionInfo(
                templateBody, declType=declType, dealWithOptional=isOptional
            )

        # This is an interface that we implement as a concrete class
        # or an XPCOM interface.

        # Allow null pointers for nullable types and old-binding classes, and
        # use an RefPtr or raw pointer for callback return values to make
        # them easier to return.
        argIsPointer = (
            type.nullable() or type.unroll().inner.isExternal() or isCallbackReturnValue
        )

        # Sequence and dictionary members, as well as owning unions (which can
        # appear here as return values in JS-implemented interfaces) have to
        # hold a strong ref to the thing being passed down.  Those all set
        # isMember.
        #
        # Also, callback return values always end up addrefing anyway, so there
        # is no point trying to avoid it here and it makes other things simpler
        # since we can assume the return value is a strong ref.
        assert not descriptor.interface.isCallback()
        forceOwningType = (isMember and isMember != "Union") or isCallbackReturnValue

        typeName = descriptor.nativeType
        typePtr = typeName + "*"

        # Compute a few things:
        #  - declType is the type we want to return as the first element of our
        #    tuple.
        #  - holderType is the type we want to return as the third element
        #    of our tuple.

        # Set up some sensible defaults for these things insofar as we can.
        holderType = None
        if argIsPointer:
            if forceOwningType:
                declType = "RefPtr<" + typeName + ">"
            else:
                declType = typePtr
        else:
            if forceOwningType:
                declType = "OwningNonNull<" + typeName + ">"
            else:
                declType = "NonNull<" + typeName + ">"

        templateBody = ""
        if forceOwningType:
            templateBody += fill(
                """
                static_assert(IsRefcounted<${typeName}>::value, "We can only store refcounted classes.");
                """,
                typeName=typeName,
            )

        if not descriptor.interface.isExternal():
            if failureCode is not None:
                templateBody += str(
                    CastableObjectUnwrapper(
                        descriptor,
                        "${val}",
                        "${maybeMutableVal}",
                        "${declName}",
                        failureCode,
                    )
                )
            else:
                templateBody += str(
                    FailureFatalCastableObjectUnwrapper(
                        descriptor,
                        "${val}",
                        "${maybeMutableVal}",
                        "${declName}",
                        exceptionCode,
                        isCallbackReturnValue,
                        firstCap(sourceDescription),
                    )
                )
        else:
            # External interface.  We always have a holder for these, because we
            # don't actually know whether we have to addref when unwrapping or not.
            # So we just pass an getter_AddRefs(RefPtr) to XPConnect and if we'll
            # need a release it'll put a non-null pointer in there.
            if forceOwningType:
                # Don't return a holderType in this case; our declName
                # will just own stuff.
                templateBody += "RefPtr<" + typeName + "> ${holderName};\n"
            else:
                holderType = "RefPtr<" + typeName + ">"
            templateBody += (
                "JS::Rooted<JSObject*> source(cx, &${val}.toObject());\n"
                + "if (NS_FAILED(UnwrapArg<"
                + typeName
                + ">(cx, source, getter_AddRefs(${holderName})))) {\n"
            )
            templateBody += CGIndenter(
                onFailureBadType(failureCode, descriptor.interface.identifier.name)
            ).define()
            templateBody += "}\n" "MOZ_ASSERT(${holderName});\n"

            # And store our value in ${declName}
            templateBody += "${declName} = ${holderName};\n"

        # Just pass failureCode, not onFailureBadType, here, so we'll report
        # the thing as not an object as opposed to not implementing whatever
        # our interface is.
        templateBody = wrapObjectTemplate(
            templateBody, type, "${declName} = nullptr;\n", failureCode
        )

        declType = CGGeneric(declType)
        if holderType is not None:
            holderType = CGGeneric(holderType)
        return JSToNativeConversionInfo(
            templateBody,
            declType=declType,
            holderType=holderType,
            dealWithOptional=isOptional,
        )

    if type.isSpiderMonkeyInterface():
        assert not isEnforceRange and not isClamp
        name = type.unroll().name  # unroll() because it may be nullable
        interfaceType = CGGeneric(name)
        declType = interfaceType
        if type.nullable():
            declType = CGTemplatedType("Nullable", declType)
            objRef = "${declName}.SetValue()"
        else:
            objRef = "${declName}"

        # Again, this is a bit strange since we are actually building a
        # template string here. ${objRef} and $*{badType} below are filled in
        # right now; $${val} expands to ${val}, to be filled in later.
        template = fill(
            """
            if (!${objRef}.Init(&$${val}.toObject())) {
              $*{badType}
            }
            """,
            objRef=objRef,
            badType=onFailureBadType(failureCode, type.name).define(),
        )
        if type.isBufferSource():
            if type.isArrayBuffer():
                isSharedMethod = "JS::IsSharedArrayBufferObject"
                isLargeMethod = "JS::IsLargeArrayBufferMaybeShared"
                isResizableMethod = "JS::IsResizableArrayBufferMaybeShared"
            else:
                assert type.isArrayBufferView() or type.isTypedArray()
                isSharedMethod = "JS::IsArrayBufferViewShared"
                isLargeMethod = "JS::IsLargeArrayBufferView"
                isResizableMethod = "JS::IsResizableArrayBufferView"
            if not isAllowShared:
                template += fill(
                    """
                    if (${isSharedMethod}(${objRef}.Obj())) {
                      $*{badType}
                    }
                    """,
                    isSharedMethod=isSharedMethod,
                    objRef=objRef,
                    badType=onFailureIsShared().define(),
                )
            # For now reject large (> 2 GB) ArrayBuffers and ArrayBufferViews.
            # Supporting this will require changing dom::TypedArray and
            # consumers.
            template += fill(
                """
                if (${isLargeMethod}(${objRef}.Obj())) {
                  $*{badType}
                }
                """,
                isLargeMethod=isLargeMethod,
                objRef=objRef,
                badType=onFailureIsLarge().define(),
            )
            # For now reject resizable ArrayBuffers and growable
            # SharedArrayBuffers. Supporting this will require changing
            # dom::TypedArray and consumers.
            template += fill(
                """
                if (${isResizableMethod}(${objRef}.Obj())) {
                  $*{badType}
                }
                """,
                isResizableMethod=isResizableMethod,
                objRef=objRef,
                badType=onFailureIsResizable().define(),
            )
        template = wrapObjectTemplate(
            template, type, "${declName}.SetNull();\n", failureCode
        )
        if not isMember or isMember == "Union":
            # This is a bit annoying.  In a union we don't want to have a
            # holder, since unions don't support that.  But if we're optional we
            # want to have a holder, so that the callee doesn't see
            # Optional<RootedSpiderMonkeyInterface<InterfaceType>>.  So do a
            # holder if we're optional and use a RootedSpiderMonkeyInterface
            # otherwise.
            if isOptional:
                holderType = CGTemplatedType(
                    "SpiderMonkeyInterfaceRooter", interfaceType
                )
                # If our SpiderMonkey interface is nullable, this will set the
                # Nullable to be not-null, but that's ok because we make an
                # explicit SetNull() call on it as needed if our JS value is
                # actually null.  XXXbz Because "Maybe" takes const refs for
                # constructor arguments, we can't pass a reference here; have
                # to pass a pointer.
                holderArgs = "cx, &%s" % objRef
                declArgs = None
            else:
                holderType = None
                holderArgs = None
                declType = CGTemplatedType("RootedSpiderMonkeyInterface", declType)
                declArgs = "cx"
        else:
            holderType = None
            holderArgs = None
            declArgs = None
        return JSToNativeConversionInfo(
            template,
            declType=declType,
            holderType=holderType,
            dealWithOptional=isOptional,
            declArgs=declArgs,
            holderArgs=holderArgs,
        )

    if type.isJSString():
        assert not isEnforceRange and not isClamp and not isAllowShared
        if type.nullable():
            raise TypeError("Nullable JSString not supported")

        declArgs = "cx"
        if isMember:
            raise TypeError("JSString not supported as member")
        else:
            declType = "JS::Rooted<JSString*>"

        if isOptional:
            raise TypeError("JSString not supported as optional")
        templateBody = fill(
            """
                if (!($${declName} = ConvertJSValueToJSString(cx, $${val}))) {
                  $*{exceptionCode}
                }
                """,
            exceptionCode=exceptionCode,
        )

        if defaultValue is not None:
            assert not isinstance(defaultValue, IDLNullValue)
            defaultCode = fill(
                """
                static const char data[] = { ${data} };
                $${declName} = JS_NewStringCopyN(cx, data, std::size(data) - 1);
                if (!$${declName}) {
                    $*{exceptionCode}
                }
                """,
                data=", ".join(
                    ["'" + char + "'" for char in defaultValue.value] + ["0"]
                ),
                exceptionCode=exceptionCode,
            )

            templateBody = handleDefault(templateBody, defaultCode)
        return JSToNativeConversionInfo(
            templateBody, declType=CGGeneric(declType), declArgs=declArgs
        )

    if type.isDOMString() or type.isUSVString() or type.isUTF8String():
        assert not isEnforceRange and not isClamp and not isAllowShared

        treatAs = {
            "Default": "eStringify",
            "EmptyString": "eEmpty",
            "Null": "eNull",
        }
        if type.nullable():
            # For nullable strings null becomes a null string.
            treatNullAs = "Null"
            # For nullable strings undefined also becomes a null string.
            undefinedBehavior = "eNull"
        else:
            undefinedBehavior = "eStringify"
            if type.legacyNullToEmptyString:
                treatNullAs = "EmptyString"
            else:
                treatNullAs = "Default"
        nullBehavior = treatAs[treatNullAs]

        def getConversionCode(varName):
            normalizeCode = ""
            if type.isUSVString():
                normalizeCode = fill(
                    """
                    if (!NormalizeUSVString(${var})) {
                      JS_ReportOutOfMemory(cx);
                      $*{exceptionCode}
                    }
                    """,
                    var=varName,
                    exceptionCode=exceptionCode,
                )

            conversionCode = fill(
                """
                if (!ConvertJSValueToString(cx, $${val}, ${nullBehavior}, ${undefinedBehavior}, ${varName})) {
                  $*{exceptionCode}
                }
                $*{normalizeCode}
                """,
                nullBehavior=nullBehavior,
                undefinedBehavior=undefinedBehavior,
                varName=varName,
                exceptionCode=exceptionCode,
                normalizeCode=normalizeCode,
            )

            if defaultValue is None:
                return conversionCode

            if isinstance(defaultValue, IDLNullValue):
                assert type.nullable()
                defaultCode = "%s.SetIsVoid(true);\n" % varName
            else:
                defaultCode = handleDefaultStringValue(
                    defaultValue, "%s.AssignLiteral" % varName
                )
            return handleDefault(conversionCode, defaultCode)

        if isMember and isMember != "Union":
            # Convert directly into the ns[C]String member we have.
            if type.isUTF8String():
                declType = "nsCString"
            else:
                declType = "nsString"
            return JSToNativeConversionInfo(
                getConversionCode("${declName}"),
                declType=CGGeneric(declType),
                dealWithOptional=isOptional,
            )

        if isOptional:
            if type.isUTF8String():
                declType = "Optional<nsACString>"
                holderType = CGGeneric("binding_detail::FakeString<char>")
            else:
                declType = "Optional<nsAString>"
                holderType = CGGeneric("binding_detail::FakeString<char16_t>")
            conversionCode = "%s" "${declName} = &${holderName};\n" % getConversionCode(
                "${holderName}"
            )
        else:
            if type.isUTF8String():
                declType = "binding_detail::FakeString<char>"
            else:
                declType = "binding_detail::FakeString<char16_t>"
            holderType = None
            conversionCode = getConversionCode("${declName}")

        # No need to deal with optional here; we handled it already
        return JSToNativeConversionInfo(
            conversionCode, declType=CGGeneric(declType), holderType=holderType
        )

    if type.isByteString():
        assert not isEnforceRange and not isClamp and not isAllowShared

        nullable = toStringBool(type.nullable())

        conversionCode = fill(
            """
            if (!ConvertJSValueToByteString(cx, $${val}, ${nullable}, "${sourceDescription}", $${declName})) {
              $*{exceptionCode}
            }
            """,
            nullable=nullable,
            sourceDescription=sourceDescription,
            exceptionCode=exceptionCode,
        )

        if defaultValue is not None:
            if isinstance(defaultValue, IDLNullValue):
                assert type.nullable()
                defaultCode = "${declName}.SetIsVoid(true);\n"
            else:
                defaultCode = handleDefaultStringValue(
                    defaultValue, "${declName}.AssignLiteral"
                )
            conversionCode = handleDefault(conversionCode, defaultCode)

        return JSToNativeConversionInfo(
            conversionCode, declType=CGGeneric("nsCString"), dealWithOptional=isOptional
        )

    if type.isEnum():
        assert not isEnforceRange and not isClamp and not isAllowShared

        enumName = type.unroll().inner.identifier.name
        declType = CGGeneric(enumName)
        if type.nullable():
            declType = CGTemplatedType("Nullable", declType)
            declType = declType.define()
            enumLoc = "${declName}.SetValue()"
        else:
            enumLoc = "${declName}"
            declType = declType.define()

        if invalidEnumValueFatal:
            handleInvalidEnumValueCode = "MOZ_ASSERT(index >= 0);\n"
        else:
            # invalidEnumValueFatal is false only for attributes.  So we won't
            # have a non-default exceptionCode here unless attribute "arg
            # conversion" code starts passing in an exceptionCode.  At which
            # point we'll need to figure out what that even means.
            assert exceptionCode == "return false;\n"
            handleInvalidEnumValueCode = dedent(
                """
                if (index < 0) {
                  return true;
                }
                """
            )

        template = fill(
            """
            {
              int index;
              if (!binding_detail::FindEnumStringIndex<${invalidEnumValueFatal}>(cx, $${val},
                                                                                 binding_detail::EnumStrings<${enumtype}>::Values,
                                                                                 "${enumtype}", "${sourceDescription}",
                                                                                 &index)) {
                $*{exceptionCode}
              }
              $*{handleInvalidEnumValueCode}
              ${enumLoc} = static_cast<${enumtype}>(index);
            }
            """,
            enumtype=enumName,
            invalidEnumValueFatal=toStringBool(invalidEnumValueFatal),
            handleInvalidEnumValueCode=handleInvalidEnumValueCode,
            exceptionCode=exceptionCode,
            enumLoc=enumLoc,
            sourceDescription=sourceDescription,
        )

        setNull = "${declName}.SetNull();\n"

        if type.nullable():
            template = CGIfElseWrapper(
                "${val}.isNullOrUndefined()", CGGeneric(setNull), CGGeneric(template)
            ).define()

        if defaultValue is not None:
            if isinstance(defaultValue, IDLNullValue):
                assert type.nullable()
                template = handleDefault(template, setNull)
            else:
                assert defaultValue.type.tag() == IDLType.Tags.domstring
                template = handleDefault(
                    template,
                    (
                        "%s = %s::%s;\n"
                        % (enumLoc, enumName, getEnumValueName(defaultValue.value))
                    ),
                )
        return JSToNativeConversionInfo(
            template, declType=CGGeneric(declType), dealWithOptional=isOptional
        )

    if type.isCallback():
        assert not isEnforceRange and not isClamp and not isAllowShared
        assert not type.treatNonCallableAsNull() or type.nullable()
        assert not type.treatNonObjectAsNull() or type.nullable()
        assert not type.treatNonObjectAsNull() or not type.treatNonCallableAsNull()

        callback = type.unroll().callback
        name = callback.identifier.name
        (declType, declArgs, conversion) = getCallbackConversionInfo(
            type, callback, isMember, isCallbackReturnValue, isOptional
        )

        if allowTreatNonCallableAsNull and type.treatNonCallableAsNull():
            haveCallable = "JS::IsCallable(&${val}.toObject())"
            if not isDefinitelyObject:
                haveCallable = "${val}.isObject() && " + haveCallable
            if defaultValue is not None:
                assert isinstance(defaultValue, IDLNullValue)
                haveCallable = "(${haveValue}) && " + haveCallable
            template = (
                ("if (%s) {\n" % haveCallable) + conversion + "} else {\n"
                "  ${declName} = nullptr;\n"
                "}\n"
            )
        elif allowTreatNonCallableAsNull and type.treatNonObjectAsNull():
            if not isDefinitelyObject:
                haveObject = "${val}.isObject()"
                if defaultValue is not None:
                    assert isinstance(defaultValue, IDLNullValue)
                    haveObject = "(${haveValue}) && " + haveObject
                template = CGIfElseWrapper(
                    haveObject,
                    CGGeneric(conversion),
                    CGGeneric("${declName} = nullptr;\n"),
                ).define()
            else:
                template = conversion
        else:
            template = wrapObjectTemplate(
                "if (JS::IsCallable(&${val}.toObject())) {\n"
                + conversion
                + "} else {\n"
                + indent(onFailureNotCallable(failureCode).define())
                + "}\n",
                type,
                "${declName} = nullptr;\n",
                failureCode,
            )
        return JSToNativeConversionInfo(
            template, declType=declType, declArgs=declArgs, dealWithOptional=isOptional
        )

    if type.isAny():
        assert not isEnforceRange and not isClamp and not isAllowShared

        declArgs = None
        if isMember in ("Variadic", "Sequence", "Dictionary", "Record"):
            # Rooting is handled by the sequence and dictionary tracers.
            declType = "JS::Value"
        else:
            assert not isMember
            declType = "JS::Rooted<JS::Value>"
            declArgs = "cx"

        assert not isOptional
        templateBody = "${declName} = ${val};\n"

        # For JS-implemented APIs, we refuse to allow passing objects that the
        # API consumer does not subsume. The extra parens around
        # ($${passedToJSImpl}) suppress unreachable code warnings when
        # $${passedToJSImpl} is the literal `false`.  But Apple is shipping a
        # buggy clang (clang 3.9) in Xcode 8.3, so there even the parens are not
        # enough.  So we manually disable some warnings in clang.
        if (
            not isinstance(descriptorProvider, Descriptor)
            or descriptorProvider.interface.isJSImplemented()
        ):
            templateBody = (
                fill(
                    """
                #ifdef __clang__
                #pragma clang diagnostic push
                #pragma clang diagnostic ignored "-Wunreachable-code"
                #pragma clang diagnostic ignored "-Wunreachable-code-return"
                #endif // __clang__
                if (($${passedToJSImpl}) && !CallerSubsumes($${val})) {
                  cx.ThrowErrorMessage<MSG_PERMISSION_DENIED_TO_PASS_ARG>("${sourceDescription}");
                  $*{exceptionCode}
                }
                #ifdef __clang__
                #pragma clang diagnostic pop
                #endif // __clang__
                """,
                    sourceDescription=sourceDescription,
                    exceptionCode=exceptionCode,
                )
                + templateBody
            )

        # We may not have a default value if we're being converted for
        # a setter, say.
        if defaultValue:
            if isinstance(defaultValue, IDLNullValue):
                defaultHandling = "${declName} = JS::NullValue();\n"
            else:
                assert isinstance(defaultValue, IDLUndefinedValue)
                defaultHandling = "${declName} = JS::UndefinedValue();\n"
            templateBody = handleDefault(templateBody, defaultHandling)
        return JSToNativeConversionInfo(
            templateBody, declType=CGGeneric(declType), declArgs=declArgs
        )

    if type.isObject():
        assert not isEnforceRange and not isClamp and not isAllowShared
        return handleJSObjectType(
            type, isMember, failureCode, exceptionCode, sourceDescription
        )

    if type.isDictionary():
        # There are no nullable dictionary-typed arguments or dictionary-typed
        # dictionary members.
        assert (
            not type.nullable()
            or isCallbackReturnValue
            or (isMember and isMember != "Dictionary")
        )
        # All optional dictionary-typed arguments always have default values,
        # but dictionary-typed dictionary members can be optional.
        assert not isOptional or isMember == "Dictionary"
        # In the callback return value case we never have to worry
        # about a default value; we always have a value.
        assert not isCallbackReturnValue or defaultValue is None

        typeName = CGDictionary.makeDictionaryName(type.unroll().inner)
        if (not isMember or isMember == "Union") and not isCallbackReturnValue:
            # Since we're not a member and not nullable or optional, no one will
            # see our real type, so we can do the fast version of the dictionary
            # that doesn't pre-initialize members.
            typeName = "binding_detail::Fast" + typeName

        declType = CGGeneric(typeName)

        # We do manual default value handling here, because we actually do want
        # a jsval, and we only handle the default-dictionary case (which we map
        # into initialization with the JS value `null`) anyway
        # NOTE: if isNullOrUndefined or isDefinitelyObject are true,
        # we know we have a value, so we don't have to worry about the
        # default value.
        if (
            not isNullOrUndefined
            and not isDefinitelyObject
            and defaultValue is not None
        ):
            assert isinstance(defaultValue, IDLDefaultDictionaryValue)
            # Initializing from JS null does the right thing to give
            # us a default-initialized dictionary.
            val = "(${haveValue}) ? ${val} : JS::NullHandleValue"
        else:
            val = "${val}"

        dictLoc = "${declName}"
        if type.nullable():
            dictLoc += ".SetValue()"

        if type.unroll().inner.needsConversionFromJS:
            args = "cx, %s, " % val
        else:
            # We can end up in this case if a dictionary that does not need
            # conversion from JS has a dictionary-typed member with a default
            # value of {}.
            args = ""
        conversionCode = fill(
            """
            if (!${dictLoc}.Init(${args}"${desc}", $${passedToJSImpl})) {
              $*{exceptionCode}
            }
            """,
            dictLoc=dictLoc,
            args=args,
            desc=firstCap(sourceDescription),
            exceptionCode=exceptionCode,
        )

        if failureCode is not None:
            # This means we're part of an overload or union conversion, and
            # should simply skip stuff if our value is not convertible to
            # dictionary, instead of trying and throwing.  If we're either
            # isDefinitelyObject or isNullOrUndefined then we're convertible to
            # dictionary and don't need to check here.
            if isDefinitelyObject or isNullOrUndefined:
                template = conversionCode
            else:
                template = fill(
                    """
                    if (!IsConvertibleToDictionary(${val})) {
                      $*{failureCode}
                    }
                    $*{conversionCode}
                    """,
                    val=val,
                    failureCode=failureCode,
                    conversionCode=conversionCode,
                )
        else:
            template = conversionCode

        if type.nullable():
            declType = CGTemplatedType("Nullable", declType)
            template = CGIfElseWrapper(
                "${val}.isNullOrUndefined()",
                CGGeneric("${declName}.SetNull();\n"),
                CGGeneric(template),
            ).define()

        # Dictionary arguments that might contain traceable things need to get
        # traced
        if (not isMember or isMember == "Union") and isCallbackReturnValue:
            # Go ahead and just convert directly into our actual return value
            declType = CGWrapper(declType, post="&")
            declArgs = "aRetVal"
        elif (not isMember or isMember == "Union") and typeNeedsRooting(type):
            declType = CGTemplatedType("RootedDictionary", declType)
            declArgs = "cx"
        else:
            declArgs = None

        return JSToNativeConversionInfo(
            template, declType=declType, declArgs=declArgs, dealWithOptional=isOptional
        )

    if type.isUndefined():
        assert not isOptional
        # This one only happens for return values, and its easy: Just
        # ignore the jsval.
        return JSToNativeConversionInfo("")

    if not type.isPrimitive():
        raise TypeError("Need conversion for argument type '%s'" % str(type))

    typeName = builtinNames[type.tag()]

    conversionBehavior = "eDefault"
    if isEnforceRange:
        assert type.isInteger()
        conversionBehavior = "eEnforceRange"
    elif isClamp:
        assert type.isInteger()
        conversionBehavior = "eClamp"

    alwaysNull = False
    if type.nullable():
        declType = CGGeneric("Nullable<" + typeName + ">")
        writeLoc = "${declName}.SetValue()"
        readLoc = "${declName}.Value()"
        nullCondition = "${val}.isNullOrUndefined()"
        if defaultValue is not None and isinstance(defaultValue, IDLNullValue):
            nullCondition = "!(${haveValue}) || " + nullCondition
            if isKnownMissing:
                alwaysNull = True
                template = dedent(
                    """
                    ${declName}.SetNull();
                    """
                )
        if not alwaysNull:
            template = fill(
                """
                if (${nullCondition}) {
                  $${declName}.SetNull();
                } else if (!ValueToPrimitive<${typeName}, ${conversionBehavior}>(cx, $${val}, "${sourceDescription}", &${writeLoc})) {
                  $*{exceptionCode}
                }
                """,
                nullCondition=nullCondition,
                typeName=typeName,
                conversionBehavior=conversionBehavior,
                sourceDescription=firstCap(sourceDescription),
                writeLoc=writeLoc,
                exceptionCode=exceptionCode,
            )
    else:
        assert defaultValue is None or not isinstance(defaultValue, IDLNullValue)
        writeLoc = "${declName}"
        readLoc = writeLoc
        template = fill(
            """
            if (!ValueToPrimitive<${typeName}, ${conversionBehavior}>(cx, $${val}, "${sourceDescription}", &${writeLoc})) {
              $*{exceptionCode}
            }
            """,
            typeName=typeName,
            conversionBehavior=conversionBehavior,
            sourceDescription=firstCap(sourceDescription),
            writeLoc=writeLoc,
            exceptionCode=exceptionCode,
        )
        declType = CGGeneric(typeName)

    if type.isFloat() and not type.isUnrestricted() and not alwaysNull:
        if lenientFloatCode is not None:
            nonFiniteCode = lenientFloatCode
        else:
            nonFiniteCode = 'cx.ThrowErrorMessage<MSG_NOT_FINITE>("%s");\n' "%s" % (
                firstCap(sourceDescription),
                exceptionCode,
            )

        # We're appending to an if-block brace, so strip trailing whitespace
        # and add an extra space before the else.
        template = template.rstrip()
        template += fill(
            """
             else if (!std::isfinite(${readLoc})) {
              $*{nonFiniteCode}
            }
            """,
            readLoc=readLoc,
            nonFiniteCode=nonFiniteCode,
        )

    if (
        defaultValue is not None
        and
        # We already handled IDLNullValue, so just deal with the other ones
        not isinstance(defaultValue, IDLNullValue)
    ):
        tag = defaultValue.type.tag()
        defaultStr = getHandleDefault(defaultValue)
        template = handleDefault(template, "%s = %s;\n" % (writeLoc, defaultStr))

    return JSToNativeConversionInfo(
        template, declType=declType, dealWithOptional=isOptional
    )


def instantiateJSToNativeConversion(info, replacements, checkForValue=False):
    """
    Take a JSToNativeConversionInfo as returned by getJSToNativeConversionInfo
    and a set of replacements as required by the strings in such an object, and
    generate code to convert into stack C++ types.

    If checkForValue is True, then the conversion will get wrapped in
    a check for ${haveValue}.
    """
    templateBody, declType, holderType, dealWithOptional = (
        info.template,
        info.declType,
        info.holderType,
        info.dealWithOptional,
    )

    if dealWithOptional and not checkForValue:
        raise TypeError("Have to deal with optional things, but don't know how")
    if checkForValue and declType is None:
        raise TypeError(
            "Need to predeclare optional things, so they will be "
            "outside the check for big enough arg count!"
        )

    # We can't precompute our holder constructor arguments, since
    # those might depend on ${declName}, which we change below.  Just
    # compute arguments at the point when we need them as we go.
    def getArgsCGThing(args):
        return CGGeneric(string.Template(args).substitute(replacements))

    result = CGList([])
    # Make a copy of "replacements" since we may be about to start modifying it
    replacements = dict(replacements)
    originalDeclName = replacements["declName"]
    if declType is not None:
        if dealWithOptional:
            replacements["declName"] = "%s.Value()" % originalDeclName
            declType = CGTemplatedType("Optional", declType)
            declCtorArgs = None
        elif info.declArgs is not None:
            declCtorArgs = CGWrapper(getArgsCGThing(info.declArgs), pre="(", post=")")
        else:
            declCtorArgs = None
        result.append(
            CGList(
                [
                    declType,
                    CGGeneric(" "),
                    CGGeneric(originalDeclName),
                    declCtorArgs,
                    CGGeneric(";\n"),
                ]
            )
        )

    originalHolderName = replacements["holderName"]
    if holderType is not None:
        if dealWithOptional:
            replacements["holderName"] = "%s.ref()" % originalHolderName
            holderType = CGTemplatedType("Maybe", holderType)
            holderCtorArgs = None
        elif info.holderArgs is not None:
            holderCtorArgs = CGWrapper(
                getArgsCGThing(info.holderArgs), pre="(", post=")"
            )
        else:
            holderCtorArgs = None
        result.append(
            CGList(
                [
                    holderType,
                    CGGeneric(" "),
                    CGGeneric(originalHolderName),
                    holderCtorArgs,
                    CGGeneric(";\n"),
                ]
            )
        )

    if "maybeMutableVal" not in replacements:
        replacements["maybeMutableVal"] = replacements["val"]

    conversion = CGGeneric(string.Template(templateBody).substitute(replacements))

    if checkForValue:
        if dealWithOptional:
            declConstruct = CGIndenter(
                CGGeneric(
                    "%s.Construct(%s);\n"
                    % (
                        originalDeclName,
                        getArgsCGThing(info.declArgs).define() if info.declArgs else "",
                    )
                )
            )
            if holderType is not None:
                holderConstruct = CGIndenter(
                    CGGeneric(
                        "%s.emplace(%s);\n"
                        % (
                            originalHolderName,
                            (
                                getArgsCGThing(info.holderArgs).define()
                                if info.holderArgs
                                else ""
                            ),
                        )
                    )
                )
            else:
                holderConstruct = None
        else:
            declConstruct = None
            holderConstruct = None

        conversion = CGList(
            [
                CGGeneric(
                    string.Template("if (${haveValue}) {\n").substitute(replacements)
                ),
                declConstruct,
                holderConstruct,
                CGIndenter(conversion),
                CGGeneric("}\n"),
            ]
        )

    result.append(conversion)
    return result


def convertConstIDLValueToJSVal(value):
    if isinstance(value, IDLNullValue):
        return "JS::NullValue()"
    if isinstance(value, IDLUndefinedValue):
        return "JS::UndefinedValue()"
    tag = value.type.tag()
    if tag in [
        IDLType.Tags.int8,
        IDLType.Tags.uint8,
        IDLType.Tags.int16,
        IDLType.Tags.uint16,
        IDLType.Tags.int32,
    ]:
        return "JS::Int32Value(%s)" % (value.value)
    if tag == IDLType.Tags.uint32:
        return "JS::NumberValue(%sU)" % (value.value)
    if tag in [IDLType.Tags.int64, IDLType.Tags.uint64]:
        return "JS::CanonicalizedDoubleValue(%s)" % numericValue(tag, value.value)
    if tag == IDLType.Tags.bool:
        return "JS::BooleanValue(%s)" % (toStringBool(value.value))
    if tag in [IDLType.Tags.float, IDLType.Tags.double]:
        return "JS::CanonicalizedDoubleValue(%s)" % (value.value)
    raise TypeError("Const value of unhandled type: %s" % value.type)


class CGArgumentConverter(CGThing):
    """
    A class that takes an IDL argument object and its index in the
    argument list and generates code to unwrap the argument to the
    right native type.

    argDescription is a description of the argument for error-reporting
    purposes.  Callers should assume that it might get placed in the middle of a
    sentence.  If it ends up at the beginning of a sentence, its first character
    will be automatically uppercased.
    """

    def __init__(
        self,
        argument,
        index,
        descriptorProvider,
        argDescription,
        member,
        invalidEnumValueFatal=True,
        lenientFloatCode=None,
    ):
        CGThing.__init__(self)
        self.argument = argument
        self.argDescription = argDescription
        assert not argument.defaultValue or argument.optional

        replacer = {"index": index, "argc": "args.length()"}
        self.replacementVariables = {
            "declName": "arg%d" % index,
            "holderName": ("arg%d" % index) + "_holder",
            "obj": "obj",
            "passedToJSImpl": toStringBool(
                isJSImplementedDescriptor(descriptorProvider)
            ),
        }
        # If we have a method generated by the maplike/setlike portion of an
        # interface, arguments can possibly be undefined, but will need to be
        # converted to the key/value type of the backing object. In this case,
        # use .get() instead of direct access to the argument. This won't
        # matter for iterable since generated functions for those interface
        # don't take arguments.
        if member.isMethod() and member.isMaplikeOrSetlikeOrIterableMethod():
            self.replacementVariables["val"] = string.Template(
                "args.get(${index})"
            ).substitute(replacer)
            self.replacementVariables["maybeMutableVal"] = string.Template(
                "args[${index}]"
            ).substitute(replacer)
        else:
            self.replacementVariables["val"] = string.Template(
                "args[${index}]"
            ).substitute(replacer)
        haveValueCheck = string.Template("args.hasDefined(${index})").substitute(
            replacer
        )
        self.replacementVariables["haveValue"] = haveValueCheck
        self.descriptorProvider = descriptorProvider
        if self.argument.canHaveMissingValue():
            self.argcAndIndex = replacer
        else:
            self.argcAndIndex = None
        self.invalidEnumValueFatal = invalidEnumValueFatal
        self.lenientFloatCode = lenientFloatCode

    def define(self):
        typeConversion = getJSToNativeConversionInfo(
            self.argument.type,
            self.descriptorProvider,
            isOptional=(self.argcAndIndex is not None and not self.argument.variadic),
            invalidEnumValueFatal=self.invalidEnumValueFatal,
            defaultValue=self.argument.defaultValue,
            lenientFloatCode=self.lenientFloatCode,
            isMember="Variadic" if self.argument.variadic else False,
            allowTreatNonCallableAsNull=self.argument.allowTreatNonCallableAsNull(),
            sourceDescription=self.argDescription,
        )

        if not self.argument.variadic:
            return instantiateJSToNativeConversion(
                typeConversion, self.replacementVariables, self.argcAndIndex is not None
            ).define()

        # Variadic arguments get turned into a sequence.
        if typeConversion.dealWithOptional:
            raise TypeError("Shouldn't have optional things in variadics")
        if typeConversion.holderType is not None:
            raise TypeError("Shouldn't need holders for variadics")

        replacer = dict(self.argcAndIndex, **self.replacementVariables)
        replacer["seqType"] = CGTemplatedType(
            "AutoSequence", typeConversion.declType
        ).define()
        if typeNeedsRooting(self.argument.type):
            rooterDecl = (
                "SequenceRooter<%s> ${holderName}(cx, &${declName});\n"
                % typeConversion.declType.define()
            )
        else:
            rooterDecl = ""
        replacer["elemType"] = typeConversion.declType.define()

        replacer["elementInitializer"] = initializerForType(self.argument.type) or ""

        # NOTE: Keep this in sync with sequence conversions as needed
        variadicConversion = string.Template(
            "${seqType} ${declName};\n"
            + rooterDecl
            + dedent(
                """
                if (${argc} > ${index}) {
                  if (!${declName}.SetCapacity(${argc} - ${index}, mozilla::fallible)) {
                    JS_ReportOutOfMemory(cx);
                    return false;
                  }
                  for (uint32_t variadicArg = ${index}; variadicArg < ${argc}; ++variadicArg) {
                    // OK to do infallible append here, since we ensured capacity already.
                    ${elemType}& slot = *${declName}.AppendElement(${elementInitializer});
                """
            )
        ).substitute(replacer)

        val = string.Template("args[variadicArg]").substitute(replacer)
        variadicConversion += indent(
            string.Template(typeConversion.template).substitute(
                {
                    "val": val,
                    "maybeMutableVal": val,
                    "declName": "slot",
                    # We only need holderName here to handle isExternal()
                    # interfaces, which use an internal holder for the
                    # conversion even when forceOwningType ends up true.
                    "holderName": "tempHolder",
                    # Use the same ${obj} as for the variadic arg itself
                    "obj": replacer["obj"],
                    "passedToJSImpl": toStringBool(
                        isJSImplementedDescriptor(self.descriptorProvider)
                    ),
                }
            ),
            4,
        )

        variadicConversion += "  }\n" "}\n"
        return variadicConversion


def getMaybeWrapValueFuncForType(type):
    if type.isJSString():
        return "MaybeWrapStringValue"
    # Callbacks might actually be DOM objects; nothing prevents a page from
    # doing that.
    if type.isCallback() or type.isCallbackInterface() or type.isObject():
        if type.nullable():
            return "MaybeWrapObjectOrNullValue"
        return "MaybeWrapObjectValue"
    # SpiderMonkey interfaces are never DOM objects.  Neither are sequences or
    # dictionaries, since those are always plain JS objects.
    if type.isSpiderMonkeyInterface() or type.isDictionary() or type.isSequence():
        if type.nullable():
            return "MaybeWrapNonDOMObjectOrNullValue"
        return "MaybeWrapNonDOMObjectValue"
    if type.isAny():
        return "MaybeWrapValue"

    # For other types, just go ahead an fall back on MaybeWrapValue for now:
    # it's always safe to do, and shouldn't be particularly slow for any of
    # them
    return "MaybeWrapValue"


sequenceWrapLevel = 0
recordWrapLevel = 0


def getWrapTemplateForType(
    type,
    descriptorProvider,
    result,
    successCode,
    returnsNewObject,
    exceptionCode,
    spiderMonkeyInterfacesAreStructs,
    isConstructorRetval=False,
):
    """
    Reflect a C++ value stored in "result", of IDL type "type" into JS.  The
    "successCode" is the code to run once we have successfully done the
    conversion and must guarantee that execution of the conversion template
    stops once the successCode has executed (e.g. by doing a 'return', or by
    doing a 'break' if the entire conversion template is inside a block that
    the 'break' will exit).

    If spiderMonkeyInterfacesAreStructs is true, then if the type is a
    SpiderMonkey interface, "result" is one of the
    dom::SpiderMonkeyInterfaceObjectStorage subclasses, not a JSObject*.

    The resulting string should be used with string.Template.  It
    needs the following keys when substituting:

      jsvalHandle: something that can be passed to methods taking a
                   JS::MutableHandle<JS::Value>.  This can be a
                   JS::MutableHandle<JS::Value> or a JS::Rooted<JS::Value>*.
      jsvalRef: something that can have .address() called on it to get a
                JS::Value* and .set() called on it to set it to a JS::Value.
                This can be a JS::MutableHandle<JS::Value> or a
                JS::Rooted<JS::Value>.
      obj: a JS::Handle<JSObject*>.

    Returns (templateString, infallibility of conversion template)
    """
    if successCode is None:
        successCode = "return true;\n"

    def setUndefined():
        return _setValue("", setter="setUndefined")

    def setNull():
        return _setValue("", setter="setNull")

    def setInt32(value):
        return _setValue(value, setter="setInt32")

    def setString(value):
        return _setValue(value, wrapAsType=type, setter="setString")

    def setObject(value, wrapAsType=None):
        return _setValue(value, wrapAsType=wrapAsType, setter="setObject")

    def setObjectOrNull(value, wrapAsType=None):
        return _setValue(value, wrapAsType=wrapAsType, setter="setObjectOrNull")

    def setUint32(value):
        return _setValue(value, setter="setNumber")

    def setDouble(value):
        return _setValue("JS_NumberValue(%s)" % value)

    def setBoolean(value):
        return _setValue(value, setter="setBoolean")

    def _setValue(value, wrapAsType=None, setter="set"):
        """
        Returns the code to set the jsval to value.

        If wrapAsType is not None, then will wrap the resulting value using the
        function that getMaybeWrapValueFuncForType(wrapAsType) returns.
        Otherwise, no wrapping will be done.
        """
        if wrapAsType is None:
            tail = successCode
        else:
            tail = fill(
                """
                if (!${maybeWrap}(cx, $${jsvalHandle})) {
                  $*{exceptionCode}
                }
                $*{successCode}
                """,
                maybeWrap=getMaybeWrapValueFuncForType(wrapAsType),
                exceptionCode=exceptionCode,
                successCode=successCode,
            )
        return ("${jsvalRef}.%s(%s);\n" % (setter, value)) + tail

    def wrapAndSetPtr(wrapCall, failureCode=None):
        """
        Returns the code to set the jsval by calling "wrapCall". "failureCode"
        is the code to run if calling "wrapCall" fails
        """
        if failureCode is None:
            failureCode = exceptionCode
        return fill(
            """
            if (!${wrapCall}) {
              $*{failureCode}
            }
            $*{successCode}
            """,
            wrapCall=wrapCall,
            failureCode=failureCode,
            successCode=successCode,
        )

    if type is None or type.isUndefined():
        return (setUndefined(), True)

    if (type.isSequence() or type.isRecord()) and type.nullable():
        # These are both wrapped in Nullable<>
        recTemplate, recInfall = getWrapTemplateForType(
            type.inner,
            descriptorProvider,
            "%s.Value()" % result,
            successCode,
            returnsNewObject,
            exceptionCode,
            spiderMonkeyInterfacesAreStructs,
        )
        code = fill(
            """

            if (${result}.IsNull()) {
              $*{setNull}
            }
            $*{recTemplate}
            """,
            result=result,
            setNull=setNull(),
            recTemplate=recTemplate,
        )
        return code, recInfall

    if type.isSequence():
        # Now do non-nullable sequences.  Our success code is just to break to
        # where we set the element in the array.  Note that we bump the
        # sequenceWrapLevel around this call so that nested sequence conversions
        # will use different iteration variables.
        global sequenceWrapLevel
        index = "sequenceIdx%d" % sequenceWrapLevel
        sequenceWrapLevel += 1
        innerTemplate = wrapForType(
            type.inner,
            descriptorProvider,
            {
                "result": "%s[%s]" % (result, index),
                "successCode": "break;\n",
                "jsvalRef": "tmp",
                "jsvalHandle": "&tmp",
                "returnsNewObject": returnsNewObject,
                "exceptionCode": exceptionCode,
                "obj": "returnArray",
                "spiderMonkeyInterfacesAreStructs": spiderMonkeyInterfacesAreStructs,
            },
        )
        sequenceWrapLevel -= 1
        code = fill(
            """

            uint32_t length = ${result}.Length();
            JS::Rooted<JSObject*> returnArray(cx, JS::NewArrayObject(cx, length));
            if (!returnArray) {
              $*{exceptionCode}
            }
            // Scope for 'tmp'
            {
              JS::Rooted<JS::Value> tmp(cx);
              for (uint32_t ${index} = 0; ${index} < length; ++${index}) {
                // Control block to let us common up the JS_DefineElement calls when there
                // are different ways to succeed at wrapping the object.
                do {
                  $*{innerTemplate}
                } while (false);
                if (!JS_DefineElement(cx, returnArray, ${index}, tmp,
                                      JSPROP_ENUMERATE)) {
                  $*{exceptionCode}
                }
              }
            }
            $*{set}
            """,
            result=result,
            exceptionCode=exceptionCode,
            index=index,
            innerTemplate=innerTemplate,
            set=setObject("*returnArray"),
        )

        return (code, False)

    if type.isRecord():
        # Now do non-nullable record.  Our success code is just to break to
        # where we define the property on the object.  Note that we bump the
        # recordWrapLevel around this call so that nested record conversions
        # will use different temp value names.
        global recordWrapLevel
        valueName = "recordValue%d" % recordWrapLevel
        recordWrapLevel += 1
        innerTemplate = wrapForType(
            type.inner,
            descriptorProvider,
            {
                "result": valueName,
                "successCode": "break;\n",
                "jsvalRef": "tmp",
                "jsvalHandle": "&tmp",
                "returnsNewObject": returnsNewObject,
                "exceptionCode": exceptionCode,
                "obj": "returnObj",
                "spiderMonkeyInterfacesAreStructs": spiderMonkeyInterfacesAreStructs,
            },
        )
        recordWrapLevel -= 1
        if type.keyType.isByteString():
            # There is no length-taking JS_DefineProperty.  So to keep
            # things sane with embedded nulls, we want to byte-inflate
            # to an nsAString.  The only byte-inflation function we
            # have around is AppendASCIItoUTF16, which luckily doesn't
            # assert anything about the input being ASCII.
            expandedKeyDecl = "NS_ConvertASCIItoUTF16 expandedKey(entry.mKey);\n"
            keyName = "expandedKey"
        elif type.keyType.isUTF8String():
            # We do the same as above for utf8 strings. We could do better if
            # we had a DefineProperty API that takes utf-8 property names.
            expandedKeyDecl = "NS_ConvertUTF8toUTF16 expandedKey(entry.mKey);\n"
            keyName = "expandedKey"
        else:
            expandedKeyDecl = ""
            keyName = "entry.mKey"

        code = fill(
            """

            JS::Rooted<JSObject*> returnObj(cx, JS_NewPlainObject(cx));
            if (!returnObj) {
              $*{exceptionCode}
            }
            // Scope for 'tmp'
            {
              JS::Rooted<JS::Value> tmp(cx);
              for (auto& entry : ${result}.Entries()) {
                auto& ${valueName} = entry.mValue;
                // Control block to let us common up the JS_DefineUCProperty calls when there
                // are different ways to succeed at wrapping the value.
                do {
                  $*{innerTemplate}
                } while (false);
                $*{expandedKeyDecl}
                if (!JS_DefineUCProperty(cx, returnObj,
                                         ${keyName}.BeginReading(),
                                         ${keyName}.Length(), tmp,
                                         JSPROP_ENUMERATE)) {
                  $*{exceptionCode}
                }
              }
            }
            $*{set}
            """,
            result=result,
            exceptionCode=exceptionCode,
            valueName=valueName,
            innerTemplate=innerTemplate,
            expandedKeyDecl=expandedKeyDecl,
            keyName=keyName,
            set=setObject("*returnObj"),
        )

        return (code, False)

    if type.isPromise():
        assert not type.nullable()
        # The use of ToJSValue here is a bit annoying because the Promise
        # version is not inlined.  But we can't put an inline version in either
        # ToJSValue.h or BindingUtils.h, because Promise.h includes ToJSValue.h
        # and that includes BindingUtils.h, so we'd get an include loop if
        # either of those headers included Promise.h.  And trying to write the
        # conversion by hand here is pretty annoying because we have to handle
        # the various RefPtr, rawptr, NonNull, etc cases, which ToJSValue will
        # handle for us.  So just eat the cost of the function call.
        return (wrapAndSetPtr("ToJSValue(cx, %s, ${jsvalHandle})" % result), False)

    if type.isGeckoInterface() and not type.isCallbackInterface():
        descriptor = descriptorProvider.getDescriptor(
            type.unroll().inner.identifier.name
        )
        if type.nullable():
            if descriptor.interface.identifier.name == "WindowProxy":
                template, infal = getWrapTemplateForType(
                    type.inner,
                    descriptorProvider,
                    "%s.Value()" % result,
                    successCode,
                    returnsNewObject,
                    exceptionCode,
                    spiderMonkeyInterfacesAreStructs,
                )
                return (
                    "if (%s.IsNull()) {\n" % result
                    + indent(setNull())
                    + "}\n"
                    + template,
                    infal,
                )

            wrappingCode = "if (!%s) {\n" % (result) + indent(setNull()) + "}\n"
        else:
            wrappingCode = ""

        if not descriptor.interface.isExternal():
            if descriptor.wrapperCache:
                wrapMethod = "GetOrCreateDOMReflector"
                wrapArgs = "cx, %s, ${jsvalHandle}" % result
            else:
                wrapMethod = "WrapNewBindingNonWrapperCachedObject"
                wrapArgs = "cx, ${obj}, %s, ${jsvalHandle}" % result
            if isConstructorRetval:
                wrapArgs += ", desiredProto"
            wrap = "%s(%s)" % (wrapMethod, wrapArgs)
            # Can only fail to wrap as a new-binding object if they already
            # threw an exception.
            failed = "MOZ_ASSERT(JS_IsExceptionPending(cx));\n" + exceptionCode
        else:
            if descriptor.notflattened:
                getIID = "&NS_GET_IID(%s), " % descriptor.nativeType
            else:
                getIID = ""
            wrap = "WrapObject(cx, %s, %s${jsvalHandle})" % (result, getIID)
            failed = None

        wrappingCode += wrapAndSetPtr(wrap, failed)
        return (wrappingCode, False)

    if type.isJSString():
        return (setString(result), False)

    if type.isDOMString() or type.isUSVString():
        if type.nullable():
            return (
                wrapAndSetPtr("xpc::StringToJsval(cx, %s, ${jsvalHandle})" % result),
                False,
            )
        else:
            return (
                wrapAndSetPtr(
                    "xpc::NonVoidStringToJsval(cx, %s, ${jsvalHandle})" % result
                ),
                False,
            )

    if type.isByteString():
        if type.nullable():
            return (
                wrapAndSetPtr("ByteStringToJsval(cx, %s, ${jsvalHandle})" % result),
                False,
            )
        else:
            return (
                wrapAndSetPtr(
                    "NonVoidByteStringToJsval(cx, %s, ${jsvalHandle})" % result
                ),
                False,
            )

    if type.isUTF8String():
        if type.nullable():
            return (
                wrapAndSetPtr("UTF8StringToJsval(cx, %s, ${jsvalHandle})" % result),
                False,
            )
        else:
            return (
                wrapAndSetPtr(
                    "NonVoidUTF8StringToJsval(cx, %s, ${jsvalHandle})" % result
                ),
                False,
            )

    if type.isEnum():
        if type.nullable():
            resultLoc = "%s.Value()" % result
        else:
            resultLoc = result
        conversion = fill(
            """
            if (!ToJSValue(cx, ${result}, $${jsvalHandle})) {
              $*{exceptionCode}
            }
            $*{successCode}
            """,
            result=resultLoc,
            exceptionCode=exceptionCode,
            successCode=successCode,
        )

        if type.nullable():
            conversion = CGIfElseWrapper(
                "%s.IsNull()" % result, CGGeneric(setNull()), CGGeneric(conversion)
            ).define()
        return conversion, False

    if type.isCallback() or type.isCallbackInterface():
        # Callbacks can store null if we nuked the compartments their
        # objects lived in.
        wrapCode = setObjectOrNull(
            "GetCallbackFromCallbackObject(cx, %(result)s)", wrapAsType=type
        )
        if type.nullable():
            wrapCode = (
                "if (%(result)s) {\n"
                + indent(wrapCode)
                + "} else {\n"
                + indent(setNull())
                + "}\n"
            )
        wrapCode = wrapCode % {"result": result}
        return wrapCode, False

    if type.isAny():
        # See comments in GetOrCreateDOMReflector explaining why we need
        # to wrap here.
        # NB: _setValue(..., type-that-is-any) calls JS_WrapValue(), so is fallible
        head = "JS::ExposeValueToActiveJS(%s);\n" % result
        return (head + _setValue(result, wrapAsType=type), False)

    if type.isObject() or (
        type.isSpiderMonkeyInterface() and not spiderMonkeyInterfacesAreStructs
    ):
        # See comments in GetOrCreateDOMReflector explaining why we need
        # to wrap here.
        if type.nullable():
            toValue = "%s"
            setter = setObjectOrNull
            head = """if (%s) {
              JS::ExposeObjectToActiveJS(%s);
            }
            """ % (
                result,
                result,
            )
        else:
            toValue = "*%s"
            setter = setObject
            head = "JS::ExposeObjectToActiveJS(%s);\n" % result
        # NB: setObject{,OrNull}(..., some-object-type) calls JS_WrapValue(), so is fallible
        return (head + setter(toValue % result, wrapAsType=type), False)

    if type.isObservableArray():
        # This first argument isn't used at all for now, the attribute getter
        # for ObservableArray type are generated in getObservableArrayGetterBody
        # instead.
        return "", False

    if not (
        type.isUnion()
        or type.isPrimitive()
        or type.isDictionary()
        or (type.isSpiderMonkeyInterface() and spiderMonkeyInterfacesAreStructs)
    ):
        raise TypeError("Need to learn to wrap %s" % type)

    if type.nullable():
        recTemplate, recInfal = getWrapTemplateForType(
            type.inner,
            descriptorProvider,
            "%s.Value()" % result,
            successCode,
            returnsNewObject,
            exceptionCode,
            spiderMonkeyInterfacesAreStructs,
        )
        return (
            "if (%s.IsNull()) {\n" % result + indent(setNull()) + "}\n" + recTemplate,
            recInfal,
        )

    if type.isSpiderMonkeyInterface():
        assert spiderMonkeyInterfacesAreStructs
        # See comments in GetOrCreateDOMReflector explaining why we need
        # to wrap here.
        # NB: setObject(..., some-object-type) calls JS_WrapValue(), so is fallible
        return (setObject("*%s.Obj()" % result, wrapAsType=type), False)

    if type.isUnion():
        return (wrapAndSetPtr("%s.ToJSVal(cx, ${obj}, ${jsvalHandle})" % result), False)

    if type.isDictionary():
        return (
            wrapAndSetPtr("%s.ToObjectInternal(cx, ${jsvalHandle})" % result),
            False,
        )

    tag = type.tag()

    if tag in [
        IDLType.Tags.int8,
        IDLType.Tags.uint8,
        IDLType.Tags.int16,
        IDLType.Tags.uint16,
        IDLType.Tags.int32,
    ]:
        return (setInt32("int32_t(%s)" % result), True)

    elif tag in [
        IDLType.Tags.int64,
        IDLType.Tags.uint64,
        IDLType.Tags.unrestricted_float,
        IDLType.Tags.float,
        IDLType.Tags.unrestricted_double,
        IDLType.Tags.double,
    ]:
        # XXXbz will cast to double do the "even significand" thing that webidl
        # calls for for 64-bit ints?  Do we care?
        return (setDouble("double(%s)" % result), True)

    elif tag == IDLType.Tags.uint32:
        return (setUint32(result), True)

    elif tag == IDLType.Tags.bool:
        return (setBoolean(result), True)

    else:
        raise TypeError("Need to learn to wrap primitive: %s" % type)


def wrapForType(type, descriptorProvider, templateValues):
    """
    Reflect a C++ value of IDL type "type" into JS.  TemplateValues is a dict
    that should contain:

      * 'jsvalRef': something that can have .address() called on it to get a
                    JS::Value* and .set() called on it to set it to a JS::Value.
                    This can be a JS::MutableHandle<JS::Value> or a
                    JS::Rooted<JS::Value>.
      * 'jsvalHandle': something that can be passed to methods taking a
                       JS::MutableHandle<JS::Value>.  This can be a
                       JS::MutableHandle<JS::Value> or a JS::Rooted<JS::Value>*.
      * 'obj' (optional): the name of the variable that contains the JSObject to
                          use as a scope when wrapping, if not supplied 'obj'
                          will be used as the name
      * 'result' (optional): the name of the variable in which the C++ value is
                             stored, if not supplied 'result' will be used as
                             the name
      * 'successCode' (optional): the code to run once we have successfully
                                  done the conversion, if not supplied 'return
                                  true;' will be used as the code.  The
                                  successCode must ensure that once it runs no
                                  more of the conversion template will be
                                  executed (e.g. by doing a 'return' or 'break'
                                  as appropriate).
      * 'returnsNewObject' (optional): If true, we're wrapping for the return
                                       value of a [NewObject] method.  Assumed
                                       false if not set.
      * 'exceptionCode' (optional): Code to run when a JS exception is thrown.
                                    The default is "return false;".  The code
                                    passed here must return.
      * 'isConstructorRetval' (optional): If true, we're wrapping a constructor
                                          return value.
    """
    wrap = getWrapTemplateForType(
        type,
        descriptorProvider,
        templateValues.get("result", "result"),
        templateValues.get("successCode", None),
        templateValues.get("returnsNewObject", False),
        templateValues.get("exceptionCode", "return false;\n"),
        templateValues.get("spiderMonkeyInterfacesAreStructs", False),
        isConstructorRetval=templateValues.get("isConstructorRetval", False),
    )[0]

    defaultValues = {"obj": "obj"}
    return string.Template(wrap).substitute(defaultValues, **templateValues)


def infallibleForMember(member, type, descriptorProvider):
    """
    Determine the fallibility of changing a C++ value of IDL type "type" into
    JS for the given attribute. Apart from returnsNewObject, all the defaults
    are used, since the fallbility does not change based on the boolean values,
    and the template will be discarded.

    CURRENT ASSUMPTIONS:
        We assume that successCode for wrapping up return values cannot contain
        failure conditions.
    """
    return getWrapTemplateForType(
        type,
        descriptorProvider,
        "result",
        None,
        memberReturnsNewObject(member),
        "return false;\n",
        False,
    )[1]


def leafTypeNeedsCx(type, retVal):
    return (
        type.isAny()
        or type.isObject()
        or type.isJSString()
        or (retVal and type.isSpiderMonkeyInterface())
    )


def leafTypeNeedsScopeObject(type, retVal):
    return retVal and type.isSpiderMonkeyInterface()


def leafTypeNeedsRooting(type):
    return leafTypeNeedsCx(type, False) or type.isSpiderMonkeyInterface()


def typeNeedsRooting(type):
    return typeMatchesLambda(type, lambda t: leafTypeNeedsRooting(t))


def typeNeedsCx(type, retVal=False):
    return typeMatchesLambda(type, lambda t: leafTypeNeedsCx(t, retVal))


def typeNeedsScopeObject(type, retVal=False):
    return typeMatchesLambda(type, lambda t: leafTypeNeedsScopeObject(t, retVal))


def typeMatchesLambda(type, func):
    if type is None:
        return False
    if type.nullable():
        return typeMatchesLambda(type.inner, func)
    if type.isSequence() or type.isRecord():
        return typeMatchesLambda(type.inner, func)
    if type.isUnion():
        return any(typeMatchesLambda(t, func) for t in type.unroll().flatMemberTypes)
    if type.isDictionary():
        return dictionaryMatchesLambda(type.inner, func)
    return func(type)


def dictionaryMatchesLambda(dictionary, func):
    return any(typeMatchesLambda(m.type, func) for m in dictionary.members) or (
        dictionary.parent and dictionaryMatchesLambda(dictionary.parent, func)
    )


# Whenever this is modified, please update CGNativeMember.getRetvalInfo as
# needed to keep the types compatible.
def getRetvalDeclarationForType(returnType, descriptorProvider, isMember=False):
    """
    Returns a tuple containing five things:

    1) A CGThing for the type of the return value, or None if there is no need
       for a return value.

    2) A value indicating the kind of ourparam to pass the value as.  Valid
       options are None to not pass as an out param at all, "ref" (to pass a
       reference as an out param), and "ptr" (to pass a pointer as an out
       param).

    3) A CGThing for a tracer for the return value, or None if no tracing is
       needed.

    4) An argument string to pass to the retval declaration
       constructor or None if there are no arguments.

    5) The name of a function that needs to be called with the return value
       before using it, or None if no function needs to be called.
    """
    if returnType is None or returnType.isUndefined():
        # Nothing to declare
        return None, None, None, None, None
    if returnType.isPrimitive() and returnType.tag() in builtinNames:
        result = CGGeneric(builtinNames[returnType.tag()])
        if returnType.nullable():
            result = CGTemplatedType("Nullable", result)
        return result, None, None, None, None
    if returnType.isJSString():
        if isMember:
            raise TypeError("JSString not supported as return type member")
        return CGGeneric("JS::Rooted<JSString*>"), "ptr", None, "cx", None
    if returnType.isDOMString() or returnType.isUSVString():
        if isMember:
            return CGGeneric("nsString"), "ref", None, None, None
        return CGGeneric("DOMString"), "ref", None, None, None
    if returnType.isByteString() or returnType.isUTF8String():
        if isMember:
            return CGGeneric("nsCString"), "ref", None, None, None
        return CGGeneric("nsAutoCString"), "ref", None, None, None
    if returnType.isEnum():
        result = CGGeneric(returnType.unroll().inner.identifier.name)
        if returnType.nullable():
            result = CGTemplatedType("Nullable", result)
        return result, None, None, None, None
    if returnType.isGeckoInterface() or returnType.isPromise():
        if returnType.isGeckoInterface():
            typeName = returnType.unroll().inner.identifier.name
            if typeName == "WindowProxy":
                result = CGGeneric("WindowProxyHolder")
                if returnType.nullable():
                    result = CGTemplatedType("Nullable", result)
                return result, None, None, None, None

            typeName = descriptorProvider.getDescriptor(typeName).nativeType
        else:
            typeName = "Promise"
        if isMember:
            conversion = None
            result = CGGeneric("StrongPtrForMember<%s>" % typeName)
        else:
            conversion = CGGeneric("StrongOrRawPtr<%s>" % typeName)
            result = CGGeneric("auto")
        return result, None, None, None, conversion
    if returnType.isCallback():
        name = returnType.unroll().callback.identifier.name
        return CGGeneric("RefPtr<%s>" % name), None, None, None, None
    if returnType.isAny():
        if isMember:
            return CGGeneric("JS::Value"), None, None, None, None
        return CGGeneric("JS::Rooted<JS::Value>"), "ptr", None, "cx", None
    if returnType.isObject() or returnType.isSpiderMonkeyInterface():
        if isMember:
            return CGGeneric("JSObject*"), None, None, None, None
        return CGGeneric("JS::Rooted<JSObject*>"), "ptr", None, "cx", None
    if returnType.isSequence():
        nullable = returnType.nullable()
        if nullable:
            returnType = returnType.inner
        result, _, _, _, _ = getRetvalDeclarationForType(
            returnType.inner, descriptorProvider, isMember="Sequence"
        )
        # While we have our inner type, set up our rooter, if needed
        if not isMember and typeNeedsRooting(returnType):
            rooter = CGGeneric(
                "SequenceRooter<%s > resultRooter(cx, &result);\n" % result.define()
            )
        else:
            rooter = None
        result = CGTemplatedType("nsTArray", result)
        if nullable:
            result = CGTemplatedType("Nullable", result)
        return result, "ref", rooter, None, None
    if returnType.isRecord():
        nullable = returnType.nullable()
        if nullable:
            returnType = returnType.inner
        result, _, _, _, _ = getRetvalDeclarationForType(
            returnType.inner, descriptorProvider, isMember="Record"
        )
        # While we have our inner type, set up our rooter, if needed
        if not isMember and typeNeedsRooting(returnType):
            rooter = CGGeneric(
                "RecordRooter<%s> resultRooter(cx, &result);\n"
                % ("nsString, " + result.define())
            )
        else:
            rooter = None
        result = CGTemplatedType("Record", [recordKeyDeclType(returnType), result])
        if nullable:
            result = CGTemplatedType("Nullable", result)
        return result, "ref", rooter, None, None
    if returnType.isDictionary():
        nullable = returnType.nullable()
        dictName = CGDictionary.makeDictionaryName(returnType.unroll().inner)
        result = CGGeneric(dictName)
        if not isMember and typeNeedsRooting(returnType):
            if nullable:
                result = CGTemplatedType("NullableRootedDictionary", result)
            else:
                result = CGTemplatedType("RootedDictionary", result)
            resultArgs = "cx"
        else:
            if nullable:
                result = CGTemplatedType("Nullable", result)
            resultArgs = None
        return result, "ref", None, resultArgs, None
    if returnType.isUnion():
        result = CGGeneric(CGUnionStruct.unionTypeName(returnType.unroll(), True))
        if not isMember and typeNeedsRooting(returnType):
            if returnType.nullable():
                result = CGTemplatedType("NullableRootedUnion", result)
            else:
                result = CGTemplatedType("RootedUnion", result)
            resultArgs = "cx"
        else:
            if returnType.nullable():
                result = CGTemplatedType("Nullable", result)
            resultArgs = None
        return result, "ref", None, resultArgs, None
    raise TypeError("Don't know how to declare return value for %s" % returnType)


def needCx(returnType, arguments, extendedAttributes, considerTypes, static=False):
    return (
        not static
        and considerTypes
        and (
            typeNeedsCx(returnType, True) or any(typeNeedsCx(a.type) for a in arguments)
        )
        or "implicitJSContext" in extendedAttributes
    )


def needScopeObject(
    returnType, arguments, extendedAttributes, isWrapperCached, considerTypes, isMember
):
    """
    isMember should be true if we're dealing with an attribute
    annotated as [StoreInSlot].
    """
    return (
        considerTypes
        and not isWrapperCached
        and (
            (not isMember and typeNeedsScopeObject(returnType, True))
            or any(typeNeedsScopeObject(a.type) for a in arguments)
        )
    )


def callerTypeGetterForDescriptor(descriptor):
    if descriptor.interface.isExposedInAnyWorker():
        systemCallerGetter = "nsContentUtils::ThreadsafeIsSystemCaller"
    else:
        systemCallerGetter = "nsContentUtils::IsSystemCaller"
    return "%s(cx) ? CallerType::System : CallerType::NonSystem" % systemCallerGetter


class CGCallGenerator(CGThing):
    """
    A class to generate an actual call to a C++ object.  Assumes that the C++
    object is stored in a variable whose name is given by the |object| argument.

    needsCallerType is a boolean indicating whether the call should receive
    a PrincipalType for the caller.

    needsErrorResult is a boolean indicating whether the call should be
    fallible and thus needs ErrorResult parameter.

    resultVar: If the returnType is not void, then the result of the call is
    stored in a C++ variable named by resultVar. The caller is responsible for
    declaring the result variable. If the caller doesn't care about the result
    value, resultVar can be omitted.

    context: The context string to pass to MaybeSetPendingException.
    """

    def __init__(
        self,
        needsErrorResult,
        needsCallerType,
        isChromeOnly,
        arguments,
        argsPre,
        returnType,
        extendedAttributes,
        descriptor,
        nativeMethodName,
        static,
        object="self",
        argsPost=[],
        resultVar=None,
        context="nullptr",
    ):
        CGThing.__init__(self)

        (
            result,
            resultOutParam,
            resultRooter,
            resultArgs,
            resultConversion,
        ) = getRetvalDeclarationForType(returnType, descriptor)

        args = CGList([CGGeneric(arg) for arg in argsPre], ", ")
        for a, name in arguments:
            arg = CGGeneric(name)

            # Now constify the things that need it
            def needsConst(a):
                if a.type.isDictionary():
                    return True
                if a.type.isSequence():
                    return True
                if a.type.isRecord():
                    return True
                # isObject() types are always a JS::Rooted, whether
                # nullable or not, and it turns out a const JS::Rooted
                # is not very helpful at all (in particular, it won't
                # even convert to a JS::Handle).
                # XXX bz Well, why not???
                if a.type.nullable() and not a.type.isObject():
                    return True
                if a.type.isString():
                    return True
                if a.canHaveMissingValue():
                    # This will need an Optional or it's a variadic;
                    # in both cases it should be const.
                    return True
                if a.type.isUnion():
                    return True
                if a.type.isSpiderMonkeyInterface():
                    return True
                return False

            if needsConst(a):
                arg = CGWrapper(arg, pre="Constify(", post=")")
            # And convert NonNull<T> to T&
            if (
                (a.type.isGeckoInterface() or a.type.isCallback() or a.type.isPromise())
                and not a.type.nullable()
            ) or a.type.isDOMString():
                arg = CGWrapper(arg, pre="NonNullHelper(", post=")")

            # If it's a refcounted object, let the static analysis know it's
            # alive for the duration of the call.
            if a.type.isGeckoInterface() or a.type.isCallback():
                arg = CGWrapper(arg, pre="MOZ_KnownLive(", post=")")

            args.append(arg)

        needResultDecl = False

        # Build up our actual call
        self.cgRoot = CGList([])

        # Return values that go in outparams go here
        if resultOutParam is not None:
            if resultVar is None:
                needResultDecl = True
                resultVar = "result"
            if resultOutParam == "ref":
                args.append(CGGeneric(resultVar))
            else:
                assert resultOutParam == "ptr"
                args.append(CGGeneric("&" + resultVar))

        needsSubjectPrincipal = "needsSubjectPrincipal" in extendedAttributes
        if needsSubjectPrincipal:
            needsNonSystemPrincipal = (
                "needsNonSystemSubjectPrincipal" in extendedAttributes
            )
            if needsNonSystemPrincipal:
                principalType = "nsIPrincipal*"
                subjectPrincipalArg = "subjectPrincipal"
                checkPrincipal = dedent(
                    """
                    if (principal->IsSystemPrincipal()) {
                      principal = nullptr;
                    }
                    """
                )
            else:
                principalType = "NonNull<nsIPrincipal>"
                subjectPrincipalArg = "NonNullHelper(subjectPrincipal)"
                checkPrincipal = ""

            self.cgRoot.append(
                CGGeneric(
                    fill(
                        """
                        ${principalType} subjectPrincipal;
                        {
                          JS::Realm* realm = js::GetContextRealm(cx);
                          MOZ_ASSERT(realm);
                          JSPrincipals* principals = JS::GetRealmPrincipals(realm);
                          nsIPrincipal* principal = nsJSPrincipals::get(principals);
                          ${checkPrincipal}
                          subjectPrincipal = principal;
                        }
                        """,
                        principalType=principalType,
                        checkPrincipal=checkPrincipal,
                    )
                )
            )

            args.append(CGGeneric("MOZ_KnownLive(%s)" % subjectPrincipalArg))

        if needsCallerType:
            if isChromeOnly:
                args.append(CGGeneric("SystemCallerGuarantee()"))
            else:
                args.append(CGGeneric(callerTypeGetterForDescriptor(descriptor)))

        canOOM = "canOOM" in extendedAttributes
        if needsErrorResult:
            args.append(CGGeneric("rv"))
        elif canOOM:
            args.append(CGGeneric("OOMReporter::From(rv)"))
        args.extend(CGGeneric(arg) for arg in argsPost)

        call = CGGeneric(nativeMethodName)
        if not static:
            call = CGWrapper(call, pre="%s->" % object)
        call = CGList([call, CGWrapper(args, pre="(", post=")")])
        if returnType is None or returnType.isUndefined() or resultOutParam is not None:
            assert resultConversion is None
            call = CGList(
                [
                    CGWrapper(
                        call,
                        pre=(
                            "// NOTE: This assert does NOT call the function.\n"
                            "static_assert(std::is_void_v<decltype("
                        ),
                        post=')>, "Should be returning void here");',
                    ),
                    call,
                ],
                "\n",
            )
        elif resultConversion is not None:
            call = CGList([resultConversion, CGWrapper(call, pre="(", post=")")])
        if resultVar is None and result is not None:
            needResultDecl = True
            resultVar = "result"

        if needResultDecl:
            if resultArgs is not None:
                resultArgsStr = "(%s)" % resultArgs
            else:
                resultArgsStr = ""
            result = CGWrapper(result, post=(" %s%s" % (resultVar, resultArgsStr)))
            if resultOutParam is None and resultArgs is None:
                call = CGList([result, CGWrapper(call, pre="(", post=")")])
            else:
                self.cgRoot.append(CGWrapper(result, post=";\n"))
                if resultOutParam is None:
                    call = CGWrapper(call, pre=resultVar + " = ")
            if resultRooter is not None:
                self.cgRoot.append(resultRooter)
        elif result is not None:
            assert resultOutParam is None
            call = CGWrapper(call, pre=resultVar + " = ")

        call = CGWrapper(call, post=";\n")
        self.cgRoot.append(call)

        if needsErrorResult or canOOM:
            self.cgRoot.prepend(CGGeneric("FastErrorResult rv;\n"))
            self.cgRoot.append(
                CGGeneric(
                    fill(
                        """
                if (MOZ_UNLIKELY(rv.MaybeSetPendingException(cx, ${context}))) {
                  return false;
                }
                """,
                        context=context,
                    )
                )
            )

        self.cgRoot.append(CGGeneric("MOZ_ASSERT(!JS_IsExceptionPending(cx));\n"))

    def define(self):
        return self.cgRoot.define()


def getUnionMemberName(type):
    # Promises can't be in unions, because they're not distinguishable
    # from anything else.
    assert not type.isPromise()
    if type.isGeckoInterface():
        return type.inner.identifier.name
    if type.isEnum():
        return type.inner.identifier.name
    return type.name


# A counter for making sure that when we're wrapping up things in
# nested sequences we don't use the same variable name to iterate over
# different sequences.
sequenceWrapLevel = 0
recordWrapLevel = 0


def wrapTypeIntoCurrentCompartment(type, value, isMember=True):
    """
    Take the thing named by "value" and if it contains "any",
    "object", or spidermonkey-interface types inside return a CGThing
    that will wrap them into the current compartment.
    """
    if type.isAny():
        assert not type.nullable()
        if isMember:
            value = "JS::MutableHandle<JS::Value>::fromMarkedLocation(&%s)" % value
        else:
            value = "&" + value
        return CGGeneric(
            "if (!JS_WrapValue(cx, %s)) {\n" "  return false;\n" "}\n" % value
        )

    if type.isObject():
        if isMember:
            value = "JS::MutableHandle<JSObject*>::fromMarkedLocation(&%s)" % value
        else:
            value = "&" + value
        return CGGeneric(
            "if (!JS_WrapObject(cx, %s)) {\n" "  return false;\n" "}\n" % value
        )

    if type.isSpiderMonkeyInterface():
        origValue = value
        if type.nullable():
            value = "%s.Value()" % value
        wrapCode = CGGeneric(
            "if (!%s.WrapIntoNewCompartment(cx)) {\n" "  return false;\n" "}\n" % value
        )
        if type.nullable():
            wrapCode = CGIfWrapper(wrapCode, "!%s.IsNull()" % origValue)
        return wrapCode

    if type.isSequence():
        origValue = value
        origType = type
        if type.nullable():
            type = type.inner
            value = "%s.Value()" % value
        global sequenceWrapLevel
        index = "indexName%d" % sequenceWrapLevel
        sequenceWrapLevel += 1
        wrapElement = wrapTypeIntoCurrentCompartment(
            type.inner, "%s[%s]" % (value, index)
        )
        sequenceWrapLevel -= 1
        if not wrapElement:
            return None
        wrapCode = CGWrapper(
            CGIndenter(wrapElement),
            pre=(
                "for (uint32_t %s = 0; %s < %s.Length(); ++%s) {\n"
                % (index, index, value, index)
            ),
            post="}\n",
        )
        if origType.nullable():
            wrapCode = CGIfWrapper(wrapCode, "!%s.IsNull()" % origValue)
        return wrapCode

    if type.isRecord():
        origType = type
        if type.nullable():
            type = type.inner
            recordRef = "%s.Value()" % value
        else:
            recordRef = value
        global recordWrapLevel
        entryRef = "mapEntry%d" % recordWrapLevel
        recordWrapLevel += 1
        wrapElement = wrapTypeIntoCurrentCompartment(type.inner, "%s.mValue" % entryRef)
        recordWrapLevel -= 1
        if not wrapElement:
            return None
        wrapCode = CGWrapper(
            CGIndenter(wrapElement),
            pre=("for (auto& %s : %s.Entries()) {\n" % (entryRef, recordRef)),
            post="}\n",
        )
        if origType.nullable():
            wrapCode = CGIfWrapper(wrapCode, "!%s.IsNull()" % value)
        return wrapCode

    if type.isDictionary():
        assert not type.nullable()
        myDict = type.inner
        memberWraps = []
        while myDict:
            for member in myDict.members:
                memberWrap = wrapArgIntoCurrentCompartment(
                    member,
                    "%s.%s"
                    % (value, CGDictionary.makeMemberName(member.identifier.name)),
                )
                if memberWrap:
                    memberWraps.append(memberWrap)
            myDict = myDict.parent
        return CGList(memberWraps) if len(memberWraps) != 0 else None

    if type.isUnion():
        origValue = value
        origType = type
        if type.nullable():
            type = type.inner
            value = "%s.Value()" % value
        memberWraps = []
        for member in type.flatMemberTypes:
            memberName = getUnionMemberName(member)
            memberWrap = wrapTypeIntoCurrentCompartment(
                member, "%s.GetAs%s()" % (value, memberName)
            )
            if memberWrap:
                memberWrap = CGIfWrapper(memberWrap, "%s.Is%s()" % (value, memberName))
                memberWraps.append(memberWrap)
        if len(memberWraps) == 0:
            return None
        wrapCode = CGList(memberWraps, "else ")
        if origType.nullable():
            wrapCode = CGIfWrapper(wrapCode, "!%s.IsNull()" % origValue)
        return wrapCode

    if (
        type.isUndefined()
        or type.isString()
        or type.isPrimitive()
        or type.isEnum()
        or type.isGeckoInterface()
        or type.isCallback()
        or type.isPromise()
    ):
        # All of these don't need wrapping.
        return None

    raise TypeError(
        "Unknown type; we don't know how to wrap it in constructor "
        "arguments: %s" % type
    )


def wrapArgIntoCurrentCompartment(arg, value, isMember=True):
    """
    As wrapTypeIntoCurrentCompartment but handles things being optional
    """
    origValue = value
    isOptional = arg.canHaveMissingValue()
    if isOptional:
        value = value + ".Value()"
    wrap = wrapTypeIntoCurrentCompartment(arg.type, value, isMember)
    if wrap and isOptional:
        wrap = CGIfWrapper(wrap, "%s.WasPassed()" % origValue)
    return wrap


def needsCallerType(m):
    return m.getExtendedAttribute("NeedsCallerType")


class CGPerSignatureCall(CGThing):
    """
    This class handles the guts of generating code for a particular
    call signature.  A call signature consists of four things:

    1) A return type, which can be None to indicate that there is no
       actual return value (e.g. this is an attribute setter) or an
       IDLType if there's an IDL type involved (including |void|).
    2) An argument list, which is allowed to be empty.
    3) A name of a native method to call. It is ignored for methods
       annotated with the "[WebExtensionStub=...]" extended attribute.
    4) Whether or not this method is static. Note that this only controls how
       the method is called (|self->nativeMethodName(...)| vs
       |nativeMethodName(...)|).

    We also need to know whether this is a method or a getter/setter
    to do error reporting correctly.

    The idlNode parameter can be either a method or an attr. We can query
    |idlNode.identifier| in both cases, so we can be agnostic between the two.

    dontSetSlot should be set to True if the value should not be cached in a
    slot (even if the attribute is marked as StoreInSlot or Cached in the
    WebIDL).

    errorReportingLabel can contain a custom label to use for error reporting.
    It will be inserted as is in the code, so if it needs to be a literal
    string in C++ it should be quoted.

    additionalArgsPre contains additional arguments that are added after the
    arguments that CGPerSignatureCall itself adds (JSContext, global, …), and
    before the actual arguments.
    """

    # XXXbz For now each entry in the argument list is either an
    # IDLArgument or a FakeArgument, but longer-term we may want to
    # have ways of flagging things like JSContext* or optional_argc in
    # there.

    def __init__(
        self,
        returnType,
        arguments,
        nativeMethodName,
        static,
        descriptor,
        idlNode,
        argConversionStartsAt=0,
        getter=False,
        setter=False,
        isConstructor=False,
        useCounterName=None,
        resultVar=None,
        objectName="obj",
        dontSetSlot=False,
        extendedAttributes=None,
        errorReportingLabel=None,
        additionalArgsPre=[],
    ):
        assert idlNode.isMethod() == (not getter and not setter)
        assert idlNode.isAttr() == (getter or setter)
        # Constructors are always static
        assert not isConstructor or static

        CGThing.__init__(self)
        self.returnType = returnType
        self.descriptor = descriptor
        self.idlNode = idlNode
        if extendedAttributes is None:
            extendedAttributes = descriptor.getExtendedAttributes(
                idlNode, getter=getter, setter=setter
            )
        self.extendedAttributes = extendedAttributes
        self.arguments = arguments
        self.argCount = len(arguments)
        self.isConstructor = isConstructor
        self.setSlot = (
            not dontSetSlot and idlNode.isAttr() and idlNode.slotIndices is not None
        )
        cgThings = []

        deprecated = idlNode.getExtendedAttribute("Deprecated") or (
            idlNode.isStatic()
            and descriptor.interface.getExtendedAttribute("Deprecated")
        )
        if deprecated:
            cgThings.append(
                CGGeneric(
                    dedent(
                        """
                DeprecationWarning(cx, obj, DeprecatedOperations::e%s);
                """
                        % deprecated[0]
                    )
                )
            )

        lenientFloatCode = None
        if idlNode.getExtendedAttribute("LenientFloat") is not None and (
            setter or idlNode.isMethod()
        ):
            cgThings.append(
                CGGeneric(
                    dedent(
                        """
                bool foundNonFiniteFloat = false;
                """
                    )
                )
            )
            lenientFloatCode = "foundNonFiniteFloat = true;\n"

        argsPre = []
        if idlNode.isStatic():
            # If we're a constructor, "obj" may not be a function, so calling
            # XrayAwareCalleeGlobal() on it is not safe.  Of course in the
            # constructor case either "obj" is an Xray or we're already in the
            # content compartment, not the Xray compartment, so just
            # constructing the GlobalObject from "obj" is fine.
            if isConstructor:
                objForGlobalObject = "obj"
            else:
                objForGlobalObject = "xpc::XrayAwareCalleeGlobal(obj)"
            cgThings.append(
                CGGeneric(
                    fill(
                        """
                GlobalObject global(cx, ${obj});
                if (global.Failed()) {
                  return false;
                }

                """,
                        obj=objForGlobalObject,
                    )
                )
            )
            argsPre.append("global")

        # For JS-implemented interfaces we do not want to base the
        # needsCx decision on the types involved, just on our extended
        # attributes. Also, JSContext is not needed for the static case
        # since GlobalObject already contains the context.
        needsCx = needCx(
            returnType,
            arguments,
            self.extendedAttributes,
            not descriptor.interface.isJSImplemented(),
            static,
        )
        if needsCx:
            argsPre.append("cx")

        needsUnwrap = False
        argsPost = []
        runConstructorInCallerCompartment = descriptor.interface.getExtendedAttribute(
            "RunConstructorInCallerCompartment"
        )
        if isConstructor and not runConstructorInCallerCompartment:
            needsUnwrap = True
            needsUnwrappedVar = False
            unwrappedVar = "obj"
            if descriptor.interface.isJSImplemented():
                # We need the desired proto in our constructor, because the
                # constructor will actually construct our reflector.
                argsPost.append("desiredProto")
        elif descriptor.interface.isJSImplemented():
            if not idlNode.isStatic():
                needsUnwrap = True
                needsUnwrappedVar = True
                argsPost.append(
                    "(unwrappedObj ? js::GetNonCCWObjectRealm(*unwrappedObj) : js::GetContextRealm(cx))"
                )
        elif needScopeObject(
            returnType,
            arguments,
            self.extendedAttributes,
            descriptor.wrapperCache,
            True,
            idlNode.getExtendedAttribute("StoreInSlot"),
        ):
            # If we ever end up with APIs like this on cross-origin objects,
            # figure out how the CheckedUnwrapDynamic bits should work.  Chances
            # are, just calling it with "cx" is fine...  For now, though, just
            # assert that it does not matter.
            assert not descriptor.isMaybeCrossOriginObject()
            # The scope object should always be from the relevant
            # global.  Make sure to unwrap it as needed.
            cgThings.append(
                CGGeneric(
                    dedent(
                        """
                JS::Rooted<JSObject*> unwrappedObj(cx, js::CheckedUnwrapStatic(obj));
                // Caller should have ensured that "obj" can be unwrapped already.
                MOZ_DIAGNOSTIC_ASSERT(unwrappedObj);
                """
                    )
                )
            )
            argsPre.append("unwrappedObj")

        if needsUnwrap and needsUnwrappedVar:
            # We cannot assign into obj because it's a Handle, not a
            # MutableHandle, so we need a separate Rooted.
            cgThings.append(CGGeneric("Maybe<JS::Rooted<JSObject*> > unwrappedObj;\n"))
            unwrappedVar = "unwrappedObj.ref()"

        if idlNode.isMethod() and idlNode.isLegacycaller():
            # If we can have legacycaller with identifier, we can't
            # just use the idlNode to determine whether we're
            # generating code for the legacycaller or not.
            assert idlNode.isIdentifierLess()
            # Pass in our thisVal
            argsPre.append("args.thisv()")

        if idlNode.isMethod():
            argDescription = "argument %(index)d"
        elif setter:
            argDescription = "value being assigned"
        else:
            assert self.argCount == 0

        if needsUnwrap:
            # It's very important that we construct our unwrappedObj, if we need
            # to do it, before we might start setting up Rooted things for our
            # arguments, so that we don't violate the stack discipline Rooted
            # depends on.
            cgThings.append(
                CGGeneric("bool objIsXray = xpc::WrapperFactory::IsXrayWrapper(obj);\n")
            )
            if needsUnwrappedVar:
                cgThings.append(
                    CGIfWrapper(
                        CGGeneric("unwrappedObj.emplace(cx, obj);\n"), "objIsXray"
                    )
                )

        for i in range(argConversionStartsAt, self.argCount):
            cgThings.append(
                CGArgumentConverter(
                    arguments[i],
                    i,
                    self.descriptor,
                    argDescription % {"index": i + 1},
                    idlNode,
                    invalidEnumValueFatal=not setter,
                    lenientFloatCode=lenientFloatCode,
                )
            )

        # Now that argument processing is done, enforce the LenientFloat stuff
        if lenientFloatCode:
            if setter:
                foundNonFiniteFloatBehavior = "return true;\n"
            else:
                assert idlNode.isMethod()
                foundNonFiniteFloatBehavior = dedent(
                    """
                    args.rval().setUndefined();
                    return true;
                    """
                )
            cgThings.append(
                CGGeneric(
                    fill(
                        """
                if (foundNonFiniteFloat) {
                  $*{returnSteps}
                }
                """,
                        returnSteps=foundNonFiniteFloatBehavior,
                    )
                )
            )

        if needsUnwrap:
            # Something depends on having the unwrapped object, so unwrap it now.
            xraySteps = []
            # XXXkhuey we should be able to MOZ_ASSERT that ${obj} is
            # not null.
            xraySteps.append(
                CGGeneric(
                    fill(
                        """
                    // Since our object is an Xray, we can just CheckedUnwrapStatic:
                    // we know Xrays have no dynamic unwrap behavior.
                    ${obj} = js::CheckedUnwrapStatic(${obj});
                    if (!${obj}) {
                      return false;
                    }
                    """,
                        obj=unwrappedVar,
                    )
                )
            )
            if isConstructor:
                # If we're called via an xray, we need to enter the underlying
                # object's compartment and then wrap up all of our arguments into
                # that compartment as needed.  This is all happening after we've
                # already done the conversions from JS values to WebIDL (C++)
                # values, so we only need to worry about cases where there are 'any'
                # or 'object' types, or other things that we represent as actual
                # JSAPI types, present.  Effectively, we're emulating a
                # CrossCompartmentWrapper, but working with the C++ types, not the
                # original list of JS::Values.
                cgThings.append(CGGeneric("Maybe<JSAutoRealm> ar;\n"))
                xraySteps.append(CGGeneric("ar.emplace(cx, obj);\n"))
                xraySteps.append(
                    CGGeneric(
                        dedent(
                            """
                    if (!JS_WrapObject(cx, &desiredProto)) {
                      return false;
                    }
                    """
                        )
                    )
                )
                xraySteps.extend(
                    wrapArgIntoCurrentCompartment(arg, argname, isMember=False)
                    for arg, argname in self.getArguments()
                )

            cgThings.append(CGIfWrapper(CGList(xraySteps), "objIsXray"))

        if idlNode.getExtendedAttribute("CEReactions") is not None and not getter:
            cgThings.append(
                CGGeneric(
                    dedent(
                        """
                Maybe<AutoCEReaction> ceReaction;
                DocGroup* docGroup = self->GetDocGroup();
                if (docGroup) {
                  ceReaction.emplace(docGroup->CustomElementReactionsStack(), cx);
                }
                """
                    )
                )
            )

        # If this is a method that was generated by a maplike/setlike
        # interface, use the maplike/setlike generator to fill in the body.
        # Otherwise, use CGCallGenerator to call the native method.
        if idlNode.isMethod() and idlNode.isMaplikeOrSetlikeOrIterableMethod():
            if (
                idlNode.maplikeOrSetlikeOrIterable.isMaplike()
                or idlNode.maplikeOrSetlikeOrIterable.isSetlike()
            ):
                cgThings.append(
                    CGMaplikeOrSetlikeMethodGenerator(
                        descriptor,
                        idlNode.maplikeOrSetlikeOrIterable,
                        idlNode.identifier.name,
                    )
                )
            else:
                cgThings.append(
                    CGIterableMethodGenerator(
                        descriptor,
                        idlNode.identifier.name,
                        self.getArgumentNames(),
                    )
                )
        elif idlNode.isAttr() and idlNode.type.isObservableArray():
            assert setter
            cgThings.append(CGObservableArraySetterGenerator(descriptor, idlNode))
        else:
            if errorReportingLabel is None:
                context = GetLabelForErrorReporting(descriptor, idlNode, isConstructor)
                if getter:
                    context = context + " getter"
                elif setter:
                    context = context + " setter"
                # Callee expects a quoted string for the context if
                # there's a context.
                context = '"%s"' % context
            else:
                context = errorReportingLabel

            if idlNode.isMethod() and idlNode.getExtendedAttribute("WebExtensionStub"):
                [
                    nativeMethodName,
                    argsPre,
                    args,
                ] = self.processWebExtensionStubAttribute(cgThings)
            else:
                args = self.getArguments()

            cgThings.append(
                CGCallGenerator(
                    self.needsErrorResult(),
                    needsCallerType(idlNode),
                    isChromeOnly(idlNode),
                    args,
                    argsPre + additionalArgsPre,
                    returnType,
                    self.extendedAttributes,
                    descriptor,
                    nativeMethodName,
                    static,
                    # We know our "self" must be being kept alive; otherwise we have
                    # a serious problem.  In common cases it's just an argument and
                    # we're MOZ_CAN_RUN_SCRIPT, but in some cases it's on the stack
                    # and being kept alive via references from JS.
                    object="MOZ_KnownLive(self)",
                    argsPost=argsPost,
                    resultVar=resultVar,
                    context=context,
                )
            )

        if useCounterName:
            # Generate a telemetry call for when [UseCounter] is used.
            windowCode = fill(
                """
                SetUseCounter(obj, eUseCounter_${useCounterName});
                """,
                useCounterName=useCounterName,
            )
            workerCode = fill(
                """
                SetUseCounter(UseCounterWorker::${useCounterName});
                """,
                useCounterName=useCounterName,
            )
            code = ""
            if idlNode.isExposedInWindow() and idlNode.isExposedInAnyWorker():
                code += fill(
                    """
                    if (NS_IsMainThread()) {
                      ${windowCode}
                    } else {
                      ${workerCode}
                    }
                    """,
                    windowCode=windowCode,
                    workerCode=workerCode,
                )
            elif idlNode.isExposedInWindow():
                code += windowCode
            elif idlNode.isExposedInAnyWorker():
                code += workerCode

            cgThings.append(CGGeneric(code))

        self.cgRoot = CGList(cgThings)

    def getArgumentNames(self):
        return ["arg" + str(i) for i in range(len(self.arguments))]

    def getArguments(self):
        return list(zip(self.arguments, self.getArgumentNames()))

    def processWebExtensionStubAttribute(self, cgThings):
        nativeMethodName = "CallWebExtMethod"
        stubNameSuffix = self.idlNode.getExtendedAttribute("WebExtensionStub")
        if isinstance(stubNameSuffix, list):
            nativeMethodName += stubNameSuffix[0]

        argsLength = len(self.getArguments())
        singleVariadicArg = argsLength == 1 and self.getArguments()[0][0].variadic

        # If the method signature does only include a single variadic arguments,
        # then `arg0` is already a Sequence of JS values and we can pass that
        # to the WebExtensions Stub method as is.
        if singleVariadicArg:
            argsPre = [
                "cx",
                'u"%s"_ns' % self.idlNode.identifier.name,
                "Constify(%s)" % "arg0",
            ]
            args = []
            return [nativeMethodName, argsPre, args]

        argsPre = [
            "cx",
            'u"%s"_ns' % self.idlNode.identifier.name,
            "Constify(%s)" % "args_sequence",
        ]
        args = []

        # Determine the maximum number of elements of the js values sequence argument,
        # skipping the last optional callback argument if any:
        #
        # if this WebExtensions API method does expect a last optional callback argument,
        # then it is the callback parameter supported for chrome-compatibility
        # reasons, and we want it as a separate argument passed to the WebExtension
        # stub method and skip it from the js values sequence including all other
        # arguments.
        maxArgsSequenceLen = argsLength
        if argsLength > 0:
            lastArg = self.getArguments()[argsLength - 1]
            isCallback = lastArg[0].type.tag() == IDLType.Tags.callback
            if isCallback and lastArg[0].optional:
                argsPre.append(
                    "MOZ_KnownLive(NonNullHelper(Constify(%s)))" % lastArg[1]
                )
                maxArgsSequenceLen = argsLength - 1

        cgThings.append(
            CGGeneric(
                dedent(
                    fill(
                        """
            // Collecting all args js values into the single sequence argument
            // passed to the webextensions stub method.
            //
            // NOTE: The stub method will receive the original non-normalized js values,
            // but those arguments will still be normalized on the main thread by the
            // WebExtensions API request handler using the same JSONSchema defnition
            // used by the non-webIDL webextensions API bindings.
            AutoSequence<JS::Value> args_sequence;
            SequenceRooter<JS::Value> args_sequence_holder(cx, &args_sequence);

            // maximum number of arguments expected by the WebExtensions API method
            // excluding the last optional chrome-compatible callback argument (which
            // is being passed to the stub method as a separate additional argument).
            uint32_t maxArgsSequenceLen = ${maxArgsSequenceLen};

            uint32_t sequenceArgsLen = args.length() <= maxArgsSequenceLen ?
              args.length() : maxArgsSequenceLen;

            if (sequenceArgsLen > 0) {
              if (!args_sequence.SetCapacity(sequenceArgsLen, mozilla::fallible)) {
                JS_ReportOutOfMemory(cx);
                return false;
              }
              for (uint32_t argIdx = 0; argIdx < sequenceArgsLen; ++argIdx) {
                // OK to do infallible append here, since we ensured capacity already.
                JS::Value& slot = *args_sequence.AppendElement();
                slot = args[argIdx];
              }
            }
            """,
                        maxArgsSequenceLen=maxArgsSequenceLen,
                    )
                )
            )
        )

        return [nativeMethodName, argsPre, args]

    def needsErrorResult(self):
        return "needsErrorResult" in self.extendedAttributes

    def wrap_return_value(self):
        wrapCode = ""

        returnsNewObject = memberReturnsNewObject(self.idlNode)
        if returnsNewObject and (
            self.returnType.isGeckoInterface() or self.returnType.isPromise()
        ):
            wrapCode += dedent(
                """
                static_assert(!std::is_pointer_v<decltype(result)>,
                              "NewObject implies that we need to keep the object alive with a strong reference.");
                """
            )

        if self.setSlot:
            # For attributes in slots, we want to do some
            # post-processing once we've wrapped them.
            successCode = "break;\n"
        else:
            successCode = None

        resultTemplateValues = {
            "jsvalRef": "args.rval()",
            "jsvalHandle": "args.rval()",
            "returnsNewObject": returnsNewObject,
            "isConstructorRetval": self.isConstructor,
            "successCode": successCode,
            # 'obj' in this dictionary is the thing whose compartment we are
            # trying to do the to-JS conversion in.  We're going to put that
            # thing in a variable named "conversionScope" if setSlot is true.
            # Otherwise, just use "obj" for lack of anything better.
            "obj": "conversionScope" if self.setSlot else "obj",
        }

        wrapCode += wrapForType(self.returnType, self.descriptor, resultTemplateValues)

        if self.setSlot:
            if self.idlNode.isStatic():
                raise TypeError(
                    "Attribute %s.%s is static, so we don't have a useful slot "
                    "to cache it in, because we don't have support for that on "
                    "interface objects.  See "
                    "https://bugzilla.mozilla.org/show_bug.cgi?id=1363870"
                    % (
                        self.descriptor.interface.identifier.name,
                        self.idlNode.identifier.name,
                    )
                )

            # When using a slot on the Xray expando, we need to make sure that
            # our initial conversion to a JS::Value is done in the caller
            # compartment.  When using a slot on our reflector, we want to do
            # the conversion in the compartment of that reflector (that is,
            # slotStorage).  In both cases we want to make sure that we finally
            # set up args.rval() to be in the caller compartment.  We also need
            # to make sure that the conversion steps happen inside a do/while
            # that they can break out of on success.
            #
            # Of course we always have to wrap the value into the slotStorage
            # compartment before we store it in slotStorage.

            # postConversionSteps are the steps that run while we're still in
            # the compartment we do our conversion in but after we've finished
            # the initial conversion into args.rval().
            postConversionSteps = ""
            if self.idlNode.getExtendedAttribute("Frozen"):
                assert (
                    self.idlNode.type.isSequence() or self.idlNode.type.isDictionary()
                )
                freezeValue = CGGeneric(
                    "JS::Rooted<JSObject*> rvalObj(cx, &args.rval().toObject());\n"
                    "if (!JS_FreezeObject(cx, rvalObj)) {\n"
                    "  return false;\n"
                    "}\n"
                )
                if self.idlNode.type.nullable():
                    freezeValue = CGIfWrapper(freezeValue, "args.rval().isObject()")
                postConversionSteps += freezeValue.define()

            # slotStorageSteps are steps that run once we have entered the
            # slotStorage compartment.
            if self.idlNode.getExtendedAttribute(
                "ReflectedHTMLAttributeReturningFrozenArray"
            ):
                storeInSlot = fill(
                    """
                    array[${arrayIndex}] = storedVal;
                    """,
                    arrayIndex=reflectedHTMLAttributesArrayIndex(
                        self.descriptor, self.idlNode
                    ),
                )
            else:
                storeInSlot = dedent(
                    """
                    JS::SetReservedSlot(slotStorage, slotIndex, storedVal);
                    """
                )

            slotStorageSteps = fill(
                """
                // Make a copy so that we don't do unnecessary wrapping on args.rval().
                JS::Rooted<JS::Value> storedVal(cx, args.rval());
                if (!${maybeWrap}(cx, &storedVal)) {
                  return false;
                }
                $*{storeInSlot}
                """,
                maybeWrap=getMaybeWrapValueFuncForType(self.idlNode.type),
                storeInSlot=storeInSlot,
            )

            checkForXray = mayUseXrayExpandoSlots(self.descriptor, self.idlNode)

            # For the case of Cached attributes, go ahead and preserve our
            # wrapper if needed.  We need to do this because otherwise the
            # wrapper could get garbage-collected and the cached value would
            # suddenly disappear, but the whole premise of cached values is that
            # they never change without explicit action on someone's part.  We
            # don't do this for StoreInSlot, since those get dealt with during
            # wrapper setup, and failure would involve us trying to clear an
            # already-preserved wrapper.
            if (
                self.idlNode.getExtendedAttribute("Cached")
                or self.idlNode.getExtendedAttribute(
                    "ReflectedHTMLAttributeReturningFrozenArray"
                )
            ) and self.descriptor.wrapperCache:
                preserveWrapper = dedent(
                    """
                    PreserveWrapper(self);
                    """
                )
                if checkForXray:
                    preserveWrapper = fill(
                        """
                        if (!isXray) {
                          // In the Xray case we don't need to do this, because getting the
                          // expando object already preserved our wrapper.
                          $*{preserveWrapper}
                        }
                        """,
                        preserveWrapper=preserveWrapper,
                    )
                slotStorageSteps += preserveWrapper

            if checkForXray:
                # In the Xray case we use the current global as conversion
                # scope, as explained in the big compartment/conversion comment
                # above.
                conversionScope = "isXray ? JS::CurrentGlobalOrNull(cx) : slotStorage"
            else:
                conversionScope = "slotStorage"

            wrapCode = fill(
                """
                {
                  JS::Rooted<JSObject*> conversionScope(cx, ${conversionScope});
                  JSAutoRealm ar(cx, conversionScope);
                  do { // block we break out of when done wrapping
                    $*{wrapCode}
                  } while (false);
                  $*{postConversionSteps}
                }
                { // And now store things in the realm of our slotStorage.
                  JSAutoRealm ar(cx, slotStorage);
                  $*{slotStorageSteps}
                }
                // And now make sure args.rval() is in the caller realm.
                return ${maybeWrap}(cx, args.rval());
                """,
                conversionScope=conversionScope,
                wrapCode=wrapCode,
                postConversionSteps=postConversionSteps,
                slotStorageSteps=slotStorageSteps,
                maybeWrap=getMaybeWrapValueFuncForType(self.idlNode.type),
            )
        return wrapCode

    def define(self):
        return self.cgRoot.define() + self.wrap_return_value()


class CGSwitch(CGList):
    """
    A class to generate code for a switch statement.

    Takes three constructor arguments: an expression, a list of cases,
    and an optional default.

    Each case is a CGCase.  The default is a CGThing for the body of
    the default case, if any.
    """

    def __init__(self, expression, cases, default=None):
        CGList.__init__(self, [CGIndenter(c) for c in cases])
        self.prepend(CGGeneric("switch (" + expression + ") {\n"))
        if default is not None:
            self.append(
                CGIndenter(
                    CGWrapper(CGIndenter(default), pre="default: {\n", post="}\n")
                )
            )

        self.append(CGGeneric("}\n"))


class CGCase(CGList):
    """
    A class to generate code for a case statement.

    Takes three constructor arguments: an expression, a CGThing for
    the body (allowed to be None if there is no body), and an optional
    argument for whether add a break, add fallthrough annotation or add nothing
    (defaulting to add a break).
    """

    ADD_BREAK = 0
    ADD_FALLTHROUGH = 1
    DONT_ADD_BREAK = 2

    def __init__(self, expression, body, breakOrFallthrough=ADD_BREAK):
        CGList.__init__(self, [])

        assert (
            breakOrFallthrough == CGCase.ADD_BREAK
            or breakOrFallthrough == CGCase.ADD_FALLTHROUGH
            or breakOrFallthrough == CGCase.DONT_ADD_BREAK
        )

        self.append(CGGeneric("case " + expression + ": {\n"))
        bodyList = CGList([body])
        if breakOrFallthrough == CGCase.ADD_FALLTHROUGH:
            bodyList.append(CGGeneric("[[fallthrough]];\n"))
        elif breakOrFallthrough == CGCase.ADD_BREAK:
            bodyList.append(CGGeneric("break;\n"))
        self.append(CGIndenter(bodyList))
        self.append(CGGeneric("}\n"))


class CGMethodCall(CGThing):
    """
    A class to generate selection of a method signature from a set of
    signatures and generation of a call to that signature.
    """

    def __init__(
        self, nativeMethodName, static, descriptor, method, isConstructor=False
    ):
        CGThing.__init__(self)

        methodName = GetLabelForErrorReporting(descriptor, method, isConstructor)
        argDesc = "argument %d"

        if method.getExtendedAttribute("UseCounter"):
            useCounterName = methodName.replace(".", "_").replace(" ", "_")
        else:
            useCounterName = None

        if method.isStatic():
            nativeType = descriptor.nativeType
            staticTypeOverride = PropertyDefiner.getStringAttr(
                method, "StaticClassOverride"
            )
            if staticTypeOverride:
                nativeType = staticTypeOverride
            nativeMethodName = "%s::%s" % (nativeType, nativeMethodName)

        def requiredArgCount(signature):
            arguments = signature[1]
            if len(arguments) == 0:
                return 0
            requiredArgs = len(arguments)
            while requiredArgs and arguments[requiredArgs - 1].optional:
                requiredArgs -= 1
            return requiredArgs

        def getPerSignatureCall(signature, argConversionStartsAt=0):
            return CGPerSignatureCall(
                signature[0],
                signature[1],
                nativeMethodName,
                static,
                descriptor,
                method,
                argConversionStartsAt=argConversionStartsAt,
                isConstructor=isConstructor,
                useCounterName=useCounterName,
            )

        signatures = method.signatures()
        if len(signatures) == 1:
            # Special case: we can just do a per-signature method call
            # here for our one signature and not worry about switching
            # on anything.
            signature = signatures[0]
            self.cgRoot = CGList([getPerSignatureCall(signature)])
            requiredArgs = requiredArgCount(signature)

            # Skip required arguments check for maplike/setlike interfaces, as
            # they can have arguments which are not passed, and are treated as
            # if undefined had been explicitly passed.
            if requiredArgs > 0 and not method.isMaplikeOrSetlikeOrIterableMethod():
                code = fill(
                    """
                    if (!args.requireAtLeast(cx, "${methodName}", ${requiredArgs})) {
                      return false;
                    }
                    """,
                    requiredArgs=requiredArgs,
                    methodName=methodName,
                )
                self.cgRoot.prepend(CGGeneric(code))
            return

        # Need to find the right overload
        maxArgCount = method.maxArgCount
        allowedArgCounts = method.allowedArgCounts

        argCountCases = []
        for argCountIdx, argCount in enumerate(allowedArgCounts):
            possibleSignatures = method.signaturesForArgCount(argCount)

            # Try to optimize away cases when the next argCount in the list
            # will have the same code as us; if it does, we can fall through to
            # that case.
            if argCountIdx + 1 < len(allowedArgCounts):
                nextPossibleSignatures = method.signaturesForArgCount(
                    allowedArgCounts[argCountIdx + 1]
                )
            else:
                nextPossibleSignatures = None
            if possibleSignatures == nextPossibleSignatures:
                # Same set of signatures means we better have the same
                # distinguishing index.  So we can in fact just fall through to
                # the next case here.
                assert len(possibleSignatures) == 1 or (
                    method.distinguishingIndexForArgCount(argCount)
                    == method.distinguishingIndexForArgCount(
                        allowedArgCounts[argCountIdx + 1]
                    )
                )
                argCountCases.append(
                    CGCase(str(argCount), None, CGCase.ADD_FALLTHROUGH)
                )
                continue

            if len(possibleSignatures) == 1:
                # easy case!
                signature = possibleSignatures[0]
                argCountCases.append(
                    CGCase(str(argCount), getPerSignatureCall(signature))
                )
                continue

            distinguishingIndex = method.distinguishingIndexForArgCount(argCount)

            def distinguishingArgument(signature):
                args = signature[1]
                if distinguishingIndex < len(args):
                    return args[distinguishingIndex]
                assert args[-1].variadic
                return args[-1]

            def distinguishingType(signature):
                return distinguishingArgument(signature).type

            for sig in possibleSignatures:
                # We should not have "any" args at distinguishingIndex,
                # since we have multiple possible signatures remaining,
                # but "any" is never distinguishable from anything else.
                assert not distinguishingType(sig).isAny()
                # We can't handle unions at the distinguishing index.
                if distinguishingType(sig).isUnion():
                    raise TypeError(
                        "No support for unions as distinguishing "
                        "arguments yet: %s" % distinguishingArgument(sig).location
                    )
                # We don't support variadics as the distinguishingArgument yet.
                # If you want to add support, consider this case:
                #
                #   undefined(long... foo);
                #   undefined(long bar, Int32Array baz);
                #
                # in which we have to convert argument 0 to long before picking
                # an overload... but all the variadic stuff needs to go into a
                # single array in case we pick that overload, so we have to have
                # machinery for converting argument 0 to long and then either
                # placing it in the variadic bit or not.  Or something.  We may
                # be able to loosen this restriction if the variadic arg is in
                # fact at distinguishingIndex, perhaps.  Would need to
                # double-check.
                if distinguishingArgument(sig).variadic:
                    raise TypeError(
                        "No support for variadics as distinguishing "
                        "arguments yet: %s" % distinguishingArgument(sig).location
                    )

            # Convert all our arguments up to the distinguishing index.
            # Doesn't matter which of the possible signatures we use, since
            # they all have the same types up to that point; just use
            # possibleSignatures[0]
            caseBody = [
                CGArgumentConverter(
                    possibleSignatures[0][1][i],
                    i,
                    descriptor,
                    argDesc % (i + 1),
                    method,
                )
                for i in range(0, distinguishingIndex)
            ]

            # Select the right overload from our set.
            distinguishingArg = "args[%d]" % distinguishingIndex

            def tryCall(
                signature, indent, isDefinitelyObject=False, isNullOrUndefined=False
            ):
                assert not isDefinitelyObject or not isNullOrUndefined
                assert isDefinitelyObject or isNullOrUndefined
                if isDefinitelyObject:
                    failureCode = "break;\n"
                else:
                    failureCode = None
                type = distinguishingType(signature)
                # The argument at index distinguishingIndex can't possibly be
                # unset here, because we've already checked that argc is large
                # enough that we can examine this argument.  But note that we
                # still want to claim that optional arguments are optional, in
                # case undefined was passed in.
                argIsOptional = distinguishingArgument(signature).canHaveMissingValue()
                testCode = instantiateJSToNativeConversion(
                    getJSToNativeConversionInfo(
                        type,
                        descriptor,
                        failureCode=failureCode,
                        isDefinitelyObject=isDefinitelyObject,
                        isNullOrUndefined=isNullOrUndefined,
                        isOptional=argIsOptional,
                        sourceDescription=(argDesc % (distinguishingIndex + 1)),
                    ),
                    {
                        "declName": "arg%d" % distinguishingIndex,
                        "holderName": ("arg%d" % distinguishingIndex) + "_holder",
                        "val": distinguishingArg,
                        "obj": "obj",
                        "haveValue": "args.hasDefined(%d)" % distinguishingIndex,
                        "passedToJSImpl": toStringBool(
                            isJSImplementedDescriptor(descriptor)
                        ),
                    },
                    checkForValue=argIsOptional,
                )
                caseBody.append(CGIndenter(testCode, indent))

                # If we got this far, we know we unwrapped to the right
                # C++ type, so just do the call.  Start conversion with
                # distinguishingIndex + 1, since we already converted
                # distinguishingIndex.
                caseBody.append(
                    CGIndenter(
                        getPerSignatureCall(signature, distinguishingIndex + 1), indent
                    )
                )

            def hasConditionalConversion(type):
                """
                Return whether the argument conversion for this type will be
                conditional on the type of incoming JS value.  For example, for
                interface types the conversion is conditional on the incoming
                value being isObject().

                For the types for which this returns false, we do not have to
                output extra isUndefined() or isNullOrUndefined() cases, because
                null/undefined values will just fall through into our
                unconditional conversion.
                """
                if type.isString() or type.isEnum():
                    return False
                if type.isBoolean():
                    distinguishingTypes = (
                        distinguishingType(s) for s in possibleSignatures
                    )
                    return any(
                        t.isString() or t.isEnum() or t.isNumeric()
                        for t in distinguishingTypes
                    )
                if type.isNumeric():
                    distinguishingTypes = (
                        distinguishingType(s) for s in possibleSignatures
                    )
                    return any(t.isString() or t.isEnum() for t in distinguishingTypes)
                return True

            def needsNullOrUndefinedCase(type):
                """
                Return true if the type needs a special isNullOrUndefined() case
                """
                return (
                    type.nullable() and hasConditionalConversion(type)
                ) or type.isDictionary()

            # First check for undefined and optional distinguishing arguments
            # and output a special branch for that case.  Note that we don't
            # use distinguishingArgument here because we actualy want to
            # exclude variadic arguments.  Also note that we skip this check if
            # we plan to output a isNullOrUndefined() special case for this
            # argument anyway, since that will subsume our isUndefined() check.
            # This is safe, because there can be at most one nullable
            # distinguishing argument, so if we're it we'll definitely get
            # picked up by the nullable handling.  Also, we can skip this check
            # if the argument has an unconditional conversion later on.
            undefSigs = [
                s
                for s in possibleSignatures
                if distinguishingIndex < len(s[1])
                and s[1][distinguishingIndex].optional
                and hasConditionalConversion(s[1][distinguishingIndex].type)
                and not needsNullOrUndefinedCase(s[1][distinguishingIndex].type)
            ]
            # Can't have multiple signatures with an optional argument at the
            # same index.
            assert len(undefSigs) < 2
            if len(undefSigs) > 0:
                caseBody.append(
                    CGGeneric("if (%s.isUndefined()) {\n" % distinguishingArg)
                )
                tryCall(undefSigs[0], 2, isNullOrUndefined=True)
                caseBody.append(CGGeneric("}\n"))

            # Next, check for null or undefined.  That means looking for
            # nullable arguments at the distinguishing index and outputting a
            # separate branch for them.  But if the nullable argument has an
            # unconditional conversion, we don't need to do that.  The reason
            # for that is that at most one argument at the distinguishing index
            # is nullable (since two nullable arguments are not
            # distinguishable), and null/undefined values will always fall
            # through to the unconditional conversion we have, if any, since
            # they will fail whatever the conditions on the input value are for
            # our other conversions.
            nullOrUndefSigs = [
                s
                for s in possibleSignatures
                if needsNullOrUndefinedCase(distinguishingType(s))
            ]
            # Can't have multiple nullable types here
            assert len(nullOrUndefSigs) < 2
            if len(nullOrUndefSigs) > 0:
                caseBody.append(
                    CGGeneric("if (%s.isNullOrUndefined()) {\n" % distinguishingArg)
                )
                tryCall(nullOrUndefSigs[0], 2, isNullOrUndefined=True)
                caseBody.append(CGGeneric("}\n"))

            # Now check for distinguishingArg being various kinds of objects.
            # The spec says to check for the following things in order:
            # 1)  A platform object that's not a platform array object, being
            #     passed to an interface or "object" arg.
            # 2)  A callable object being passed to a callback or "object" arg.
            # 3)  An iterable object being passed to a sequence arg.
            # 4)  Any object being passed to a array or callback interface or
            #     dictionary or "object" arg.

            # First grab all the overloads that have a non-callback interface
            # (which includes SpiderMonkey interfaces) at the distinguishing
            # index.  We can also include the ones that have an "object" here,
            # since if those are present no other object-typed argument will
            # be.
            objectSigs = [
                s
                for s in possibleSignatures
                if (
                    distinguishingType(s).isObject()
                    or distinguishingType(s).isNonCallbackInterface()
                )
            ]

            # And all the overloads that take callbacks
            objectSigs.extend(
                s for s in possibleSignatures if distinguishingType(s).isCallback()
            )

            # And all the overloads that take sequences
            objectSigs.extend(
                s for s in possibleSignatures if distinguishingType(s).isSequence()
            )

            # Now append all the overloads that take a dictionary or callback
            # interface or record.  There should be only one of these!
            genericObjectSigs = [
                s
                for s in possibleSignatures
                if (
                    distinguishingType(s).isDictionary()
                    or distinguishingType(s).isRecord()
                    or distinguishingType(s).isCallbackInterface()
                )
            ]
            assert len(genericObjectSigs) <= 1
            objectSigs.extend(genericObjectSigs)

            # There might be more than one thing in objectSigs; we need to check
            # which ones we unwrap to.
            if len(objectSigs) > 0:
                # Here it's enough to guard on our argument being an object.
                # The code for unwrapping non-callback interfaces, spiderMonkey
                # interfaces, and sequences will just bail out and move
                # on to the next overload if the object fails to unwrap
                # correctly, while "object" accepts any object anyway.  We
                # could even not do the isObject() check up front here, but in
                # cases where we have multiple object overloads it makes sense
                # to do it only once instead of for each overload.  That will
                # also allow the unwrapping test to skip having to do codegen
                # for the null-or-undefined case, which we already handled
                # above.
                caseBody.append(CGGeneric("if (%s.isObject()) {\n" % distinguishingArg))
                for sig in objectSigs:
                    caseBody.append(CGIndenter(CGGeneric("do {\n")))
                    # Indent by 4, since we need to indent further
                    # than our "do" statement
                    tryCall(sig, 4, isDefinitelyObject=True)
                    caseBody.append(CGIndenter(CGGeneric("} while (false);\n")))

                caseBody.append(CGGeneric("}\n"))

            # Now we only have to consider booleans, numerics, and strings.  If
            # we only have one of them, then we can just output it.  But if not,
            # then we need to output some of the cases conditionally: if we have
            # a string overload, then boolean and numeric are conditional, and
            # if not then boolean is conditional if we have a numeric overload.
            def findUniqueSignature(filterLambda):
                sigs = [s for s in possibleSignatures if filterLambda(s)]
                assert len(sigs) < 2
                if len(sigs) > 0:
                    return sigs[0]
                return None

            stringSignature = findUniqueSignature(
                lambda s: (
                    distinguishingType(s).isString() or distinguishingType(s).isEnum()
                )
            )
            numericSignature = findUniqueSignature(
                lambda s: distinguishingType(s).isNumeric()
            )
            booleanSignature = findUniqueSignature(
                lambda s: distinguishingType(s).isBoolean()
            )

            if stringSignature or numericSignature:
                booleanCondition = "%s.isBoolean()"
            else:
                booleanCondition = None

            if stringSignature:
                numericCondition = "%s.isNumber()"
            else:
                numericCondition = None

            def addCase(sig, condition):
                sigCode = getPerSignatureCall(sig, distinguishingIndex)
                if condition:
                    sigCode = CGIfWrapper(sigCode, condition % distinguishingArg)
                caseBody.append(sigCode)

            if booleanSignature:
                addCase(booleanSignature, booleanCondition)
            if numericSignature:
                addCase(numericSignature, numericCondition)
            if stringSignature:
                addCase(stringSignature, None)

            if not booleanSignature and not numericSignature and not stringSignature:
                # Just throw; we have no idea what we're supposed to
                # do with this.
                caseBody.append(
                    CGGeneric(
                        'return cx.ThrowErrorMessage<MSG_OVERLOAD_RESOLUTION_FAILED>("%d", "%d");\n'
                        % (distinguishingIndex + 1, argCount)
                    )
                )

            argCountCases.append(CGCase(str(argCount), CGList(caseBody)))

        overloadCGThings = []
        overloadCGThings.append(
            CGGeneric(
                "unsigned argcount = std::min(args.length(), %du);\n" % maxArgCount
            )
        )
        overloadCGThings.append(
            CGSwitch(
                "argcount",
                argCountCases,
                CGGeneric(
                    dedent(
                        """
                         // Using nsPrintfCString here would require including that
                         // header.  Let's not worry about it.
                         nsAutoCString argCountStr;
                         argCountStr.AppendPrintf("%u", args.length());
                         return cx.ThrowErrorMessage<MSG_INVALID_OVERLOAD_ARGCOUNT>(argCountStr.get());
                         """
                    )
                ),
            )
        )
        overloadCGThings.append(
            CGGeneric(
                'MOZ_CRASH("We have an always-returning default case");\n'
                "return false;\n"
            )
        )
        self.cgRoot = CGList(overloadCGThings)

    def define(self):
        return self.cgRoot.define()


class CGGetterCall(CGPerSignatureCall):
    """
    A class to generate a native object getter call for a particular IDL
    getter.
    """

    def __init__(
        self,
        returnType,
        nativeMethodName,
        descriptor,
        attr,
        errorReportingLabel=None,
        argsPre=[],
        dontSetSlot=False,
        extendedAttributes=None,
        preConversionCode=None,
    ):
        self.preConversionCode = preConversionCode
        if attr.getExtendedAttribute("UseCounter"):
            useCounterName = "%s_%s_getter" % (
                descriptor.interface.identifier.name,
                attr.identifier.name,
            )
        else:
            useCounterName = None
        if attr.isStatic():
            nativeMethodName = "%s::%s" % (descriptor.nativeType, nativeMethodName)
        CGPerSignatureCall.__init__(
            self,
            returnType,
            [],
            nativeMethodName,
            attr.isStatic(),
            descriptor,
            attr,
            getter=True,
            useCounterName=useCounterName,
            dontSetSlot=dontSetSlot,
            extendedAttributes=extendedAttributes,
            errorReportingLabel=errorReportingLabel,
            additionalArgsPre=argsPre,
        )

    def wrap_return_value(self):
        wrap = CGPerSignatureCall.wrap_return_value(self)
        if self.preConversionCode is not None:
            wrap = self.preConversionCode + wrap
        return wrap


class FakeIdentifier:
    def __init__(self, name):
        self.name = name


class FakeArgument:
    """
    A class that quacks like an IDLArgument.  This is used to make
    setters look like method calls or for special operations.
    """

    def __init__(self, type, name="arg", allowTreatNonCallableAsNull=False):
        self.type = type
        self.optional = False
        self.variadic = False
        self.defaultValue = None
        self._allowTreatNonCallableAsNull = allowTreatNonCallableAsNull

        self.identifier = FakeIdentifier(name)

    def allowTreatNonCallableAsNull(self):
        return self._allowTreatNonCallableAsNull

    def canHaveMissingValue(self):
        return False


class CGSetterCall(CGPerSignatureCall):
    """
    A class to generate a native object setter call for a particular IDL
    setter.
    """

    def __init__(
        self,
        argType,
        nativeMethodName,
        descriptor,
        attr,
        errorReportingLabel=None,
        argsPre=[],
    ):
        if attr.getExtendedAttribute("UseCounter"):
            useCounterName = "%s_%s_setter" % (
                descriptor.interface.identifier.name,
                attr.identifier.name,
            )
        else:
            useCounterName = None
        if attr.isStatic():
            nativeMethodName = "%s::%s" % (descriptor.nativeType, nativeMethodName)
        CGPerSignatureCall.__init__(
            self,
            None,
            [FakeArgument(argType, allowTreatNonCallableAsNull=True)],
            nativeMethodName,
            attr.isStatic(),
            descriptor,
            attr,
            setter=True,
            useCounterName=useCounterName,
            errorReportingLabel=errorReportingLabel,
            additionalArgsPre=argsPre,
        )

    def wrap_return_value(self):
        attr = self.idlNode
        clearSlot = ""
        if self.descriptor.wrapperCache and attr.slotIndices is not None:
            if attr.getExtendedAttribute("StoreInSlot"):
                clearSlot = "%s(cx, self);\n" % MakeClearCachedValueNativeName(
                    self.idlNode
                )
            elif attr.getExtendedAttribute("Cached"):
                clearSlot = "%s(self);\n" % MakeClearCachedValueNativeName(self.idlNode)

        # We have no return value
        return "\n" "%s" "return true;\n" % clearSlot


class CGAbstractBindingMethod(CGAbstractStaticMethod):
    """
    Common class to generate some of our class hooks.  This will generate the
    function declaration, get a reference to the JS object for our binding
    object (which might be an argument of the class hook or something we get
    from a JS::CallArgs), and unwrap into the right C++ type. Subclasses are
    expected to override the generate_code function to do the rest of the work.
    This function should return a CGThing which is already properly indented.

    getThisObj should be code for getting a JSObject* for the binding
    object.  "" can be passed in if the binding object is already stored in
    'obj'.

    callArgs should be code for getting a JS::CallArgs into a variable
    called 'args'.  This can be "" if there is already such a variable
    around or if the body does not need a JS::CallArgs.

    """

    def __init__(
        self,
        descriptor,
        name,
        args,
        getThisObj,
        callArgs="JS::CallArgs args = JS::CallArgsFromVp(argc, vp);\n",
    ):
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

        # This can't ever happen, because we only use this for class hooks.
        self.unwrapFailureCode = fill(
            """
            MOZ_CRASH("Unexpected object in '${name}' hook");
            return false;
            """,
            name=name,
        )

        if getThisObj == "":
            self.getThisObj = None
        else:
            self.getThisObj = CGGeneric(
                "JS::Rooted<JSObject*> obj(cx, %s);\n" % getThisObj
            )
        self.callArgs = callArgs

    def definition_body(self):
        body = self.callArgs
        if self.getThisObj is not None:
            body += self.getThisObj.define() + "\n"
        body += "%s* self;\n" % self.descriptor.nativeType
        body += dedent(
            """
            JS::Rooted<JS::Value> rootSelf(cx, JS::ObjectValue(*obj));
            """
        )

        body += str(
            CastableObjectUnwrapper(
                self.descriptor, "rootSelf", "&rootSelf", "self", self.unwrapFailureCode
            )
        )

        return body + self.generate_code().define()

    def generate_code(self):
        assert False  # Override me


class CGAbstractStaticBindingMethod(CGAbstractStaticMethod):
    """
    Common class to generate the JSNatives for all our static methods, getters
    and setters.  This will generate the function declaration and unwrap the
    global object.  Subclasses are expected to override the generate_code
    function to do the rest of the work.  This function should return a
    CGThing which is already properly indented.
    """

    def __init__(self, descriptor, name):
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", JSNativeArguments(), canRunScript=True
        )

    def definition_body(self):
        # Make sure that "obj" is in the same compartment as "cx", since we'll
        # later use it to wrap return values.
        unwrap = dedent(
            """
            JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
            JS::Rooted<JSObject*> obj(cx, &args.callee());

            """
        )
        return unwrap + self.generate_code().define()

    def generate_code(self):
        assert False  # Override me


def MakeNativeName(name):
    return name[0].upper() + IDLToCIdentifier(name[1:])


def GetWebExposedName(idlObject, descriptor):
    if idlObject == descriptor.operations["Stringifier"]:
        return "toString"
    name = idlObject.identifier.name
    if name == "__namedsetter":
        return "named setter"
    if name == "__namedgetter":
        return "named getter"
    if name == "__indexedsetter":
        return "indexed setter"
    if name == "__indexedgetter":
        return "indexed getter"
    if name == "__legacycaller":
        return "legacy caller"
    return name


def GetConstructorNameForReporting(descriptor, ctor):
    # Figure out the name of our constructor for reporting purposes.
    # For unnamed webidl constructors, identifier.name is "constructor" but
    # the name JS sees is the interface name; for legacy factory functions
    # identifier.name is the actual name.
    ctorName = ctor.identifier.name
    if ctorName == "constructor":
        return descriptor.interface.identifier.name
    return ctorName


def GetLabelForErrorReporting(descriptor, idlObject, isConstructor):
    """
    descriptor is the descriptor for the interface involved

    idlObject is the method (regular or static), attribute (regular or
    static), or constructor (named or not) involved.

    isConstructor is true if idlObject is a constructor and false otherwise.
    """
    if isConstructor:
        return "%s constructor" % GetConstructorNameForReporting(descriptor, idlObject)

    namePrefix = descriptor.interface.identifier.name
    name = GetWebExposedName(idlObject, descriptor)
    if " " in name:
        # It's got a space already, so just space-separate.
        return "%s %s" % (namePrefix, name)

    return "%s.%s" % (namePrefix, name)


class CGSpecializedMethod(CGAbstractStaticMethod):
    """
    A class for generating the C++ code for a specialized method that the JIT
    can call with lower overhead.
    """

    def __init__(self, descriptor, method):
        self.method = method
        name = CppKeywords.checkMethodName(IDLToCIdentifier(method.identifier.name))
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("const JSJitMethodCallArgs&", "args"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

    def definition_body(self):
        nativeName = CGSpecializedMethod.makeNativeName(self.descriptor, self.method)
        call = CGMethodCall(
            nativeName, self.method.isStatic(), self.descriptor, self.method
        ).define()
        prefix = ""
        if self.method.getExtendedAttribute("CrossOriginCallable"):
            for signature in self.method.signatures():
                # non-undefined signatures would require us to deal with remote proxies for the
                # return value here.
                if not signature[0].isUndefined():
                    raise TypeError(
                        "We don't support a method marked as CrossOriginCallable "
                        "with non-undefined return type"
                    )
            prototypeID, _ = PrototypeIDAndDepth(self.descriptor)
            prefix = fill(
                """
                // CrossOriginThisPolicy::UnwrapThisObject stores a ${nativeType}::RemoteProxy in void_self
                // if obj is a proxy with a RemoteObjectProxy handler for the right type, or else it stores
                // a ${nativeType}. If we get here from the JIT (without going through UnwrapThisObject) we
                // know void_self contains a ${nativeType}; we don't have special cases in the JIT to deal
                // with remote object proxies.
                if (IsRemoteObjectProxy(obj, ${prototypeID})) {
                    auto* self = static_cast<${nativeType}::RemoteProxy*>(void_self);
                    $*{call}
                }
                """,
                prototypeID=prototypeID,
                nativeType=self.descriptor.nativeType,
                call=call,
            )
        return prefix + fill(
            """
            auto* self = static_cast<${nativeType}*>(void_self);
            $*{call}
            """,
            nativeType=self.descriptor.nativeType,
            call=call,
        )

    def auto_profiler_label(self):
        interface_name = self.descriptor.interface.identifier.name
        method_name = self.method.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", "${method_name}", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_METHOD) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            method_name=method_name,
        )

    @staticmethod
    def should_have_method_description(descriptor, idlMethod):
        """
        Returns whether the given IDL method (static, non-static, constructor)
        should have a method description declaration, for use in error
        reporting.
        """
        # If a method has overloads, it needs a method description, because it
        # can throw MSG_INVALID_OVERLOAD_ARGCOUNT at the very least.
        if len(idlMethod.signatures()) != 1:
            return True

        # Methods with only one signature need a method description if one of
        # their args needs it.
        sig = idlMethod.signatures()[0]
        args = sig[1]
        return any(
            idlTypeNeedsCallContext(
                arg.type,
                descriptor,
                allowTreatNonCallableAsNull=arg.allowTreatNonCallableAsNull(),
            )
            for arg in args
        )

    @staticmethod
    def error_reporting_label_helper(descriptor, idlMethod, isConstructor):
        """
        Returns the method description to use for error reporting for the given
        IDL method.  Used to implement common error_reporting_label() functions
        across different classes.
        """
        if not CGSpecializedMethod.should_have_method_description(
            descriptor, idlMethod
        ):
            return None
        return '"%s"' % GetLabelForErrorReporting(descriptor, idlMethod, isConstructor)

    def error_reporting_label(self):
        return CGSpecializedMethod.error_reporting_label_helper(
            self.descriptor, self.method, isConstructor=False
        )

    @staticmethod
    def makeNativeName(descriptor, method):
        if method.underlyingAttr:
            return CGSpecializedGetterCommon.makeNativeName(
                descriptor, method.underlyingAttr
            )
        name = method.identifier.name
        return MakeNativeName(descriptor.binaryNameFor(name, method.isStatic()))


class CGMethodPromiseWrapper(CGAbstractStaticMethod):
    """
    A class for generating a wrapper around another method that will
    convert exceptions to promises.
    """

    def __init__(self, descriptor, methodToWrap):
        self.method = methodToWrap
        name = self.makeName(methodToWrap.name)
        args = list(methodToWrap.args)
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

    def definition_body(self):
        return fill(
            """
            bool ok = ${methodName}(${args});
            if (ok) {
              return true;
            }
            return ConvertExceptionToPromise(cx, args.rval());
            """,
            methodName=self.method.name,
            args=", ".join(arg.name for arg in self.args),
        )

    @staticmethod
    def makeName(methodName):
        return methodName + "_promiseWrapper"


class CGDefaultToJSONMethod(CGSpecializedMethod):
    def __init__(self, descriptor, method):
        assert method.isDefaultToJSON()
        CGSpecializedMethod.__init__(self, descriptor, method)

    def definition_body(self):
        ret = fill(
            """
            auto* self = static_cast<${nativeType}*>(void_self);
            JS::Rooted<JSObject*> result(cx, JS_NewPlainObject(cx));
            if (!result) {
              return false;
            }
            """,
            nativeType=self.descriptor.nativeType,
        )

        jsonDescriptors = [self.descriptor]
        interface = self.descriptor.interface.parent
        while interface:
            descriptor = self.descriptor.getDescriptor(interface.identifier.name)
            if descriptor.hasDefaultToJSON:
                jsonDescriptors.append(descriptor)
            interface = interface.parent

        # Iterate the array in reverse: oldest ancestor first
        for descriptor in jsonDescriptors[::-1]:
            ret += fill(
                """
                if (!${parentclass}::CollectJSONAttributes(cx, obj, MOZ_KnownLive(self), result)) {
                  return false;
                }
                """,
                parentclass=toBindingNamespace(descriptor.name),
            )
        ret += "args.rval().setObject(*result);\n" "return true;\n"
        return ret


class CGLegacyCallHook(CGAbstractBindingMethod):
    """
    Call hook for our object
    """

    def __init__(self, descriptor):
        self._legacycaller = descriptor.operations["LegacyCaller"]
        # Our "self" is actually the callee in this case, not the thisval.
        CGAbstractBindingMethod.__init__(
            self,
            descriptor,
            LEGACYCALLER_HOOK_NAME,
            JSNativeArguments(),
            getThisObj="&args.callee()",
        )

    def define(self):
        if not self._legacycaller:
            return ""
        return CGAbstractBindingMethod.define(self)

    def generate_code(self):
        name = self._legacycaller.identifier.name
        nativeName = MakeNativeName(self.descriptor.binaryNameFor(name, False))
        return CGMethodCall(nativeName, False, self.descriptor, self._legacycaller)

    def error_reporting_label(self):
        # Should act like methods.
        return CGSpecializedMethod.error_reporting_label_helper(
            self.descriptor, self._legacycaller, isConstructor=False
        )


class CGResolveHook(CGAbstractClassHook):
    """
    Resolve hook for objects that have the NeedResolve extended attribute.
    """

    def __init__(self, descriptor):
        assert descriptor.interface.getExtendedAttribute("NeedResolve")

        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("JS::Handle<jsid>", "id"),
            Argument("bool*", "resolvedp"),
        ]
        CGAbstractClassHook.__init__(self, descriptor, RESOLVE_HOOK_NAME, "bool", args)

    def generate_code(self):
        return dedent(
            """
            JS::Rooted<mozilla::Maybe<JS::PropertyDescriptor>> desc(cx);
            if (!self->DoResolve(cx, obj, id, &desc)) {
              return false;
            }
            if (desc.isNothing()) {
              return true;
            }
            // If desc.value() is undefined, then the DoResolve call
            // has already defined it on the object.  Don't try to also
            // define it.
            MOZ_ASSERT(desc->isDataDescriptor());
            if (!desc->value().isUndefined()) {
              JS::Rooted<JS::PropertyDescriptor> defineDesc(cx, *desc);
              defineDesc.setResolving(true);
              if (!JS_DefinePropertyById(cx, obj, id, defineDesc)) {
                return false;
              }
            }
            *resolvedp = true;
            return true;
            """
        )

    def definition_body(self):
        if self.descriptor.isGlobal():
            # Resolve standard classes
            prefix = dedent(
                """
                if (!ResolveGlobal(cx, obj, id, resolvedp)) {
                  return false;
                }
                if (*resolvedp) {
                  return true;
                }

                """
            )
        else:
            prefix = ""
        return prefix + CGAbstractClassHook.definition_body(self)


class CGMayResolveHook(CGAbstractStaticMethod):
    """
    Resolve hook for objects that have the NeedResolve extended attribute.
    """

    def __init__(self, descriptor):
        assert descriptor.interface.getExtendedAttribute("NeedResolve")

        args = [
            Argument("const JSAtomState&", "names"),
            Argument("jsid", "id"),
            Argument("JSObject*", "maybeObj"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, MAY_RESOLVE_HOOK_NAME, "bool", args
        )

    def definition_body(self):
        if self.descriptor.isGlobal():
            # Check whether this would resolve as a standard class.
            prefix = dedent(
                """
                if (MayResolveGlobal(names, id, maybeObj)) {
                  return true;
                }

                """
            )
        else:
            prefix = ""
        return prefix + "return %s::MayResolve(id);\n" % self.descriptor.nativeType


class CGEnumerateHook(CGAbstractBindingMethod):
    """
    Enumerate hook for objects with custom hooks.
    """

    def __init__(self, descriptor):
        assert descriptor.interface.getExtendedAttribute("NeedResolve")

        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("JS::MutableHandleVector<jsid>", "properties"),
            Argument("bool", "enumerableOnly"),
        ]
        # Our "self" is actually the "obj" argument in this case, not the thisval.
        CGAbstractBindingMethod.__init__(
            self, descriptor, NEW_ENUMERATE_HOOK_NAME, args, getThisObj="", callArgs=""
        )

    def generate_code(self):
        return CGGeneric(
            dedent(
                """
            FastErrorResult rv;
            self->GetOwnPropertyNames(cx, properties, enumerableOnly, rv);
            if (rv.MaybeSetPendingException(cx)) {
              return false;
            }
            return true;
            """
            )
        )

    def definition_body(self):
        if self.descriptor.isGlobal():
            # Enumerate standard classes
            prefix = dedent(
                """
                if (!EnumerateGlobal(cx, obj, properties, enumerableOnly)) {
                  return false;
                }

                """
            )
        else:
            prefix = ""
        return prefix + CGAbstractBindingMethod.definition_body(self)


class CppKeywords:
    """
    A class for checking if method names declared in webidl
    are not in conflict with C++ keywords.
    """

    keywords = frozenset(
        [
            "alignas",
            "alignof",
            "and",
            "and_eq",
            "asm",
            "assert",
            "auto",
            "bitand",
            "bitor",
            "bool",
            "break",
            "case",
            "catch",
            "char",
            "char16_t",
            "char32_t",
            "class",
            "compl",
            "const",
            "constexpr",
            "const_cast",
            "continue",
            "decltype",
            "default",
            "delete",
            "do",
            "double",
            "dynamic_cast",
            "else",
            "enum",
            "explicit",
            "export",
            "extern",
            "false",
            "final",
            "float",
            "for",
            "friend",
            "goto",
            "if",
            "inline",
            "int",
            "long",
            "mutable",
            "namespace",
            "new",
            "noexcept",
            "not",
            "not_eq",
            "nullptr",
            "operator",
            "or",
            "or_eq",
            "override",
            "private",
            "protected",
            "public",
            "register",
            "reinterpret_cast",
            "return",
            "short",
            "signed",
            "sizeof",
            "static",
            "static_assert",
            "static_cast",
            "struct",
            "switch",
            "template",
            "this",
            "thread_local",
            "throw",
            "true",
            "try",
            "typedef",
            "typeid",
            "typename",
            "union",
            "unsigned",
            "using",
            "virtual",
            "void",
            "volatile",
            "wchar_t",
            "while",
            "xor",
            "xor_eq",
        ]
    )

    @staticmethod
    def checkMethodName(name):
        # Double '_' because 'assert' and '_assert' cannot be used in MS2013 compiler.
        # Bug 964892 and bug 963560.
        if name in CppKeywords.keywords:
            name = "_" + name + "_"
        return name


class CGStaticMethod(CGAbstractStaticBindingMethod):
    """
    A class for generating the C++ code for an IDL static method.
    """

    def __init__(self, descriptor, method):
        self.method = method
        name = CppKeywords.checkMethodName(IDLToCIdentifier(method.identifier.name))
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name)

    def generate_code(self):
        nativeName = CGSpecializedMethod.makeNativeName(self.descriptor, self.method)
        return CGMethodCall(nativeName, True, self.descriptor, self.method)

    def auto_profiler_label(self):
        interface_name = self.descriptor.interface.identifier.name
        method_name = self.method.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", "${method_name}", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_METHOD) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            method_name=method_name,
        )

    def error_reporting_label(self):
        return CGSpecializedMethod.error_reporting_label_helper(
            self.descriptor, self.method, isConstructor=False
        )


class CGSpecializedGetterCommon(CGAbstractStaticMethod):
    """
    A class for generating the code for a specialized attribute getter
    that the JIT can call with lower overhead.
    """

    def __init__(
        self,
        descriptor,
        name,
        nativeName,
        attr,
        args,
        errorReportingLabel=None,
        additionalArg=None,
    ):
        self.nativeName = nativeName
        self.errorReportingLabel = errorReportingLabel
        self.additionalArgs = [] if additionalArg is None else [additionalArg]
        # StoreInSlot attributes have their getters called from Wrap().  We
        # really hope they can't run script, and don't want to annotate Wrap()
        # methods as doing that anyway, so let's not annotate them as
        # MOZ_CAN_RUN_SCRIPT.
        CGAbstractStaticMethod.__init__(
            self,
            descriptor,
            name,
            "bool",
            args + self.additionalArgs,
            canRunScript=not attr.getExtendedAttribute("StoreInSlot"),
        )

    def definition_body(self):
        prefix = fill(
            """
            auto* self = static_cast<${nativeType}*>(void_self);
            """,
            nativeType=self.descriptor.nativeType,
        )

        if self.attr.isMaplikeOrSetlikeAttr():
            assert not self.attr.getExtendedAttribute("CrossOriginReadable")
            # If the interface is maplike/setlike, there will be one getter
            # method for the size property of the backing object. Due to having
            # to unpack the backing object from the slot, this requires its own
            # generator.
            return prefix + getMaplikeOrSetlikeSizeGetterBody(
                self.descriptor, self.attr
            )

        if self.attr.type.isObservableArray():
            assert not self.attr.getExtendedAttribute("CrossOriginReadable")
            # If the attribute is observableArray, due to having to unpack the
            # backing object from the slot, this requires its own generator.
            return prefix + getObservableArrayGetterBody(self.descriptor, self.attr)

        if self.nativeName is None:
            nativeName = CGSpecializedGetterCommon.makeNativeName(
                self.descriptor, self.attr
            )
        else:
            nativeName = self.nativeName

        type = self.attr.type
        if self.attr.getExtendedAttribute("CrossOriginReadable"):
            remoteType = type
            extendedAttributes = self.descriptor.getExtendedAttributes(
                self.attr, getter=True
            )
            if (
                remoteType.isGeckoInterface()
                and not remoteType.unroll().inner.isExternal()
                and remoteType.unroll().inner.getExtendedAttribute("ChromeOnly") is None
            ):
                # We'll use a JSObject. It might make more sense to use remoteType's
                # RemoteProxy, but it's not easy to construct a type for that from here.
                remoteType = BuiltinTypes[IDLBuiltinType.Types.object]
                if "needsErrorResult" not in extendedAttributes:
                    extendedAttributes.append("needsErrorResult")
            prototypeID, _ = PrototypeIDAndDepth(self.descriptor)
            prefix = (
                fill(
                    """
                if (IsRemoteObjectProxy(obj, ${prototypeID})) {
                    ${nativeType}::RemoteProxy* self = static_cast<${nativeType}::RemoteProxy*>(void_self);
                    $*{call}
                }
            """,
                    prototypeID=prototypeID,
                    nativeType=self.descriptor.nativeType,
                    call=CGGetterCall(
                        remoteType,
                        nativeName,
                        self.descriptor,
                        self.attr,
                        self.errorReportingLabel,
                        argsPre=[a.name for a in self.additionalArgs],
                        dontSetSlot=True,
                        extendedAttributes=extendedAttributes,
                    ).define(),
                )
                + prefix
            )

        argsPre = [a.name for a in self.additionalArgs]
        maybeReturnCachedVal = None
        if self.attr.slotIndices is not None:
            # We're going to store this return value in a slot on some object,
            # to cache it.  The question is, which object?  For dictionary and
            # sequence return values, we want to use a slot on the Xray expando
            # if we're called via Xrays, and a slot on our reflector otherwise.
            # On the other hand, when dealing with some interface types
            # (e.g. window.document) we want to avoid calling the getter more
            # than once.  In the case of window.document, it's because the
            # getter can start returning null, which would get hidden in the
            # non-Xray case by the fact that it's [StoreOnSlot], so the cached
            # version is always around.
            #
            # The upshot is that we use the reflector slot for any getter whose
            # type is a gecko interface, whether we're called via Xrays or not.
            # Since [Cached] and [StoreInSlot] cannot be used with "NewObject",
            # we know that in the interface type case the returned object is
            # wrappercached.  So creating Xrays to it is reasonable.
            if mayUseXrayExpandoSlots(self.descriptor, self.attr):
                prefix += dedent(
                    """
                    // Have to either root across the getter call or reget after.
                    bool isXray;
                    JS::Rooted<JSObject*> slotStorage(cx, GetCachedSlotStorageObject(cx, obj, &isXray));
                    if (!slotStorage) {
                      return false;
                    }
                    """
                )
            else:
                prefix += dedent(
                    """
                    // Have to either root across the getter call or reget after.
                    JS::Rooted<JSObject*> slotStorage(cx, js::UncheckedUnwrap(obj, /* stopAtWindowProxy = */ false));
                    MOZ_ASSERT(IsDOMObject(slotStorage));
                    """
                )

            if self.attr.getExtendedAttribute(
                "ReflectedHTMLAttributeReturningFrozenArray"
            ):
                argsPre.append("hasCachedValue ? &useCachedValue : nullptr")
                isXray = (
                    "isXray"
                    if mayUseXrayExpandoSlots(self.descriptor, self.attr)
                    else "false"
                )
                prefix += fill(
                    """
                    auto& array = ReflectedHTMLAttributeSlots::GetOrCreate(slotStorage, ${isXray});
                    JS::Rooted<JS::Value> cachedVal(cx, array[${arrayIndex}]);
                    bool hasCachedValue = !cachedVal.isUndefined();
                    bool useCachedValue = false;
                    """,
                    isXray=isXray,
                    arrayIndex=reflectedHTMLAttributesArrayIndex(
                        self.descriptor, self.attr
                    ),
                )
                maybeReturnCachedVal = fill(
                    """
                    MOZ_ASSERT_IF(useCachedValue, hasCachedValue);
                    if (hasCachedValue && useCachedValue) {
                      args.rval().set(cachedVal);
                      // The cached value is in the compartment of slotStorage,
                      // so wrap into the caller compartment as needed.
                      return ${maybeWrap}(cx, args.rval());
                    }

                    ${clearCachedValue}(self);

                    """,
                    maybeWrap=getMaybeWrapValueFuncForType(self.attr.type),
                    clearCachedValue=MakeClearCachedValueNativeName(self.attr),
                )
            else:
                if mayUseXrayExpandoSlots(self.descriptor, self.attr):
                    prefix += fill(
                        """
                        const size_t slotIndex = isXray ? ${xraySlotIndex} : ${slotIndex};
                        """,
                        xraySlotIndex=memberXrayExpandoReservedSlot(
                            self.attr, self.descriptor
                        ),
                        slotIndex=memberReservedSlot(self.attr, self.descriptor),
                    )
                else:
                    prefix += fill(
                        """
                        const size_t slotIndex = ${slotIndex};
                        """,
                        slotIndex=memberReservedSlot(self.attr, self.descriptor),
                    )
                prefix += fill(
                    """
                    MOZ_ASSERT(slotIndex < JSCLASS_RESERVED_SLOTS(JS::GetClass(slotStorage)));
                    {
                      // Scope for cachedVal
                      JS::Value cachedVal = JS::GetReservedSlot(slotStorage, slotIndex);
                      if (!cachedVal.isUndefined()) {
                        args.rval().set(cachedVal);
                        // The cached value is in the compartment of slotStorage,
                        // so wrap into the caller compartment as needed.
                        return ${maybeWrap}(cx, args.rval());
                      }
                    }

                    """,
                    maybeWrap=getMaybeWrapValueFuncForType(self.attr.type),
                )

        return (
            prefix
            + CGGetterCall(
                type,
                nativeName,
                self.descriptor,
                self.attr,
                self.errorReportingLabel,
                argsPre=argsPre,
                preConversionCode=maybeReturnCachedVal,
            ).define()
        )

    def auto_profiler_label(self, profilerLabel=None):
        if profilerLabel is None:
            profilerLabel = '"' + self.attr.identifier.name + '"'
        interface_name = self.descriptor.interface.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", ${attr_name}, DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_GETTER) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            attr_name=profilerLabel,
        )

    def error_reporting_label(self):
        # Getters never need a BindingCallContext.
        return None

    @staticmethod
    def makeNativeName(descriptor, attr):
        name = attr.identifier.name
        nativeName = MakeNativeName(descriptor.binaryNameFor(name, attr.isStatic()))
        _, resultOutParam, _, _, _ = getRetvalDeclarationForType(attr.type, descriptor)
        extendedAttrs = descriptor.getExtendedAttributes(attr, getter=True)
        canFail = "needsErrorResult" in extendedAttrs or "canOOM" in extendedAttrs
        if resultOutParam or attr.type.nullable() or canFail:
            nativeName = "Get" + nativeName
        return nativeName


class CGSpecializedGetter(CGSpecializedGetterCommon):
    """
    A class for generating the code for a specialized attribute getter
    that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        self.attr = attr
        name = "get_" + IDLToCIdentifier(attr.identifier.name)
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitGetterCallArgs", "args"),
        ]
        CGSpecializedGetterCommon.__init__(self, descriptor, name, None, attr, args)


class CGTemplateForSpecializedGetter(CGSpecializedGetterCommon):
    """
    A class for generating the code for a specialized attribute getter
    that can be used as the common getter that templated attribute
    getters can forward to.
    """

    def __init__(self, descriptor, template):
        self.attr = template.attr
        self.attrNameString = template.attrNameString
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitGetterCallArgs", "args"),
        ]
        errorDescription = (
            'ErrorDescriptionFor<ErrorFor::getter>{ "%s", attrName }'
            % descriptor.interface.identifier.name
        )
        CGSpecializedGetterCommon.__init__(
            self,
            descriptor,
            template.getter,
            template.getter,
            self.attr,
            args,
            errorReportingLabel=errorDescription,
            additionalArg=Argument(template.argument.type, template.argument.name),
        )

    def auto_profiler_label(self):
        return (
            fill(
                """
                const char* attrName = ${attrNameString};
                """,
                attrNameString=self.attrNameString,
            )
            + CGSpecializedGetterCommon.auto_profiler_label(self, "attrName")
        )


class CGSpecializedTemplatedGetter(CGAbstractStaticMethod):
    """
    A class for generating the code for a specialized templated attribute
    getter that forwards to a common template getter.
    """

    def __init__(self, descriptor, attr, template, additionalArg):
        self.attr = attr
        self.template = template
        self.additionalArg = additionalArg
        name = "get_" + IDLToCIdentifier(attr.identifier.name)
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitGetterCallArgs", "args"),
        ]
        assert not attr.getExtendedAttribute("StoreInSlot")
        CGAbstractStaticMethod.__init__(
            self,
            descriptor,
            name,
            "bool",
            args,
            canRunScript=True,
        )

    def definition_body(self):
        if self.additionalArg is None:
            additionalArg = self.attr.identifier.name
        else:
            additionalArg = self.additionalArg

        return fill(
            """
            return ${namespace}::${getter}(cx, obj, void_self, args, ${additionalArg});
            """,
            namespace=toBindingNamespace(
                self.template.descriptor.interface.identifier.name
            ),
            getter=self.template.getter,
            additionalArg=additionalArg,
        )


class CGGetterPromiseWrapper(CGAbstractStaticMethod):
    """
    A class for generating a wrapper around another getter that will
    convert exceptions to promises.
    """

    def __init__(self, descriptor, getterToWrap):
        self.getter = getterToWrap
        name = self.makeName(getterToWrap.name)
        args = list(getterToWrap.args)
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

    def definition_body(self):
        return fill(
            """
            bool ok = ${getterName}(${args});
            if (ok) {
              return true;
            }
            return ConvertExceptionToPromise(cx, args.rval());
            """,
            getterName=self.getter.name,
            args=", ".join(arg.name for arg in self.args),
        )

    @staticmethod
    def makeName(getterName):
        return getterName + "_promiseWrapper"


class CGStaticGetter(CGAbstractStaticBindingMethod):
    """
    A class for generating the C++ code for an IDL static attribute getter.
    """

    def __init__(self, descriptor, attr):
        self.attr = attr
        name = "get_" + IDLToCIdentifier(attr.identifier.name)
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name)

    def generate_code(self):
        nativeName = CGSpecializedGetterCommon.makeNativeName(
            self.descriptor, self.attr
        )
        return CGGetterCall(self.attr.type, nativeName, self.descriptor, self.attr)

    def auto_profiler_label(self):
        interface_name = self.descriptor.interface.identifier.name
        attr_name = self.attr.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", "${attr_name}", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_GETTER) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            attr_name=attr_name,
        )

    def error_reporting_label(self):
        # Getters never need a BindingCallContext.
        return None


class CGSpecializedSetterCommon(CGAbstractStaticMethod):
    """
    A class for generating the code for a specialized attribute setter
    that the JIT can call with lower overhead.
    """

    def __init__(
        self,
        descriptor,
        name,
        nativeName,
        attr,
        args,
        errorReportingLabel=None,
        additionalArg=None,
    ):
        self.nativeName = nativeName
        self.errorReportingLabel = errorReportingLabel
        self.additionalArgs = [] if additionalArg is None else [additionalArg]
        CGAbstractStaticMethod.__init__(
            self,
            descriptor,
            name,
            "bool",
            args + self.additionalArgs,
            canRunScript=True,
        )

    def definition_body(self):
        type = self.attr.type
        call = CGSetterCall(
            type,
            self.nativeName,
            self.descriptor,
            self.attr,
            self.errorReportingLabel,
            [a.name for a in self.additionalArgs],
        ).define()
        prefix = ""
        if self.attr.getExtendedAttribute("CrossOriginWritable"):
            if type.isGeckoInterface() and not type.unroll().inner.isExternal():
                # a setter taking a Gecko interface would require us to deal with remote
                # proxies for the value here.
                raise TypeError(
                    "We don't support the setter of %s marked as "
                    "CrossOriginWritable because it takes a Gecko interface "
                    "as the value",
                    self.attr.identifier.name,
                )
            prototypeID, _ = PrototypeIDAndDepth(self.descriptor)
            prefix = fill(
                """
                if (IsRemoteObjectProxy(obj, ${prototypeID})) {
                    auto* self = static_cast<${nativeType}::RemoteProxy*>(void_self);
                    $*{call}
                }
                """,
                prototypeID=prototypeID,
                nativeType=self.descriptor.nativeType,
                call=call,
            )

        return prefix + fill(
            """
            auto* self = static_cast<${nativeType}*>(void_self);
            $*{call}
            """,
            nativeType=self.descriptor.nativeType,
            call=call,
        )

    def auto_profiler_label(self, profilerLabel=None):
        interface_name = self.descriptor.interface.identifier.name
        if profilerLabel is None:
            profilerLabel = '"' + self.attr.identifier.name + '"'
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", ${attr_name}, DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_SETTER) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            attr_name=profilerLabel,
        )

    @staticmethod
    def error_reporting_label_helper(descriptor, attr):
        # Setters need a BindingCallContext if the type of the attribute needs
        # one.
        if not idlTypeNeedsCallContext(
            attr.type, descriptor, allowTreatNonCallableAsNull=True
        ):
            return None
        return '"%s"' % (
            GetLabelForErrorReporting(descriptor, attr, isConstructor=False) + " setter"
        )

    def error_reporting_label(self):
        errorReportingLabel = CGSpecializedSetterCommon.error_reporting_label_helper(
            self.descriptor, self.attr
        )
        if errorReportingLabel is None:
            return None
        if self.errorReportingLabel:
            return self.errorReportingLabel
        return errorReportingLabel

    @staticmethod
    def makeNativeName(descriptor, attr):
        name = attr.identifier.name
        return "Set" + MakeNativeName(descriptor.binaryNameFor(name, attr.isStatic()))


class CGSpecializedSetter(CGSpecializedSetterCommon):
    """
    A class for generating the code for a specialized attribute setter
    that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        self.attr = attr
        name = "set_" + IDLToCIdentifier(attr.identifier.name)
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitSetterCallArgs", "args"),
        ]
        CGSpecializedSetterCommon.__init__(
            self,
            descriptor,
            name,
            CGSpecializedSetterCommon.makeNativeName(descriptor, attr),
            attr,
            args,
        )


class CGTemplateForSpecializedSetter(CGSpecializedSetterCommon):
    """
    A class for generating the code for a specialized attribute setter
    that can be used as the common setter that templated attribute
    setters can forward to.
    """

    def __init__(self, descriptor, template):
        self.attr = template.attr
        self.attrNameString = template.attrNameString
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitSetterCallArgs", "args"),
        ]
        errorDescription = (
            'ErrorDescriptionFor<ErrorFor::setter>{ "%s", attrName }'
            % descriptor.interface.identifier.name
        )
        CGSpecializedSetterCommon.__init__(
            self,
            descriptor,
            template.setter,
            template.setter,
            self.attr,
            args,
            errorReportingLabel=errorDescription,
            additionalArg=Argument(template.argument.type, template.argument.name),
        )

    def auto_profiler_label(self):
        return (
            fill(
                """
                const char* attrName = ${attrNameString};
                """,
                attrNameString=self.attrNameString,
            )
            + CGSpecializedSetterCommon.auto_profiler_label(self, "attrName")
        )


class CGSpecializedTemplatedSetter(CGAbstractStaticMethod):
    """
    A class for generating the code for a specialized templated attribute
    setter that forwards to a common template setter.
    """

    def __init__(self, descriptor, attr, template, additionalArg):
        self.attr = attr
        self.template = template
        self.additionalArg = additionalArg
        name = "set_" + IDLToCIdentifier(attr.identifier.name)
        args = [
            Argument("JSContext*", "cx"),
            Argument("JS::Handle<JSObject*>", "obj"),
            Argument("void*", "void_self"),
            Argument("JSJitSetterCallArgs", "args"),
        ]
        CGAbstractStaticMethod.__init__(
            self, descriptor, name, "bool", args, canRunScript=True
        )

    def definition_body(self):
        additionalArgs = []
        if self.additionalArg is None:
            additionalArgs.append(self.attr.identifier.name)
        else:
            additionalArgs.append(self.additionalArg)

        return fill(
            """
            return ${namespace}::${setter}(cx, obj, void_self, args, ${additionalArgs});
            """,
            namespace=toBindingNamespace(
                self.template.descriptor.interface.identifier.name
            ),
            setter=self.template.setter,
            additionalArgs=", ".join(additionalArgs),
        )


class CGStaticSetter(CGAbstractStaticBindingMethod):
    """
    A class for generating the C++ code for an IDL static attribute setter.
    """

    def __init__(self, descriptor, attr):
        self.attr = attr
        name = "set_" + IDLToCIdentifier(attr.identifier.name)
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name)

    def generate_code(self):
        nativeName = CGSpecializedSetterCommon.makeNativeName(
            self.descriptor, self.attr
        )
        checkForArg = CGGeneric(
            fill(
                """
            if (!args.requireAtLeast(cx, "${name} setter", 1)) {
              return false;
            }
            """,
                name=self.attr.identifier.name,
            )
        )
        call = CGSetterCall(self.attr.type, nativeName, self.descriptor, self.attr)
        return CGList([checkForArg, call])

    def auto_profiler_label(self):
        interface_name = self.descriptor.interface.identifier.name
        attr_name = self.attr.identifier.name
        return fill(
            """
            AUTO_PROFILER_LABEL_DYNAMIC_FAST(
              "${interface_name}", "${attr_name}", DOM, cx,
              uint32_t(js::ProfilingStackFrame::Flags::STRING_TEMPLATE_SETTER) |
              uint32_t(js::ProfilingStackFrame::Flags::RELEVANT_FOR_JS));
            """,
            interface_name=interface_name,
            attr_name=attr_name,
        )

    def error_reporting_label(self):
        return CGSpecializedSetterCommon.error_reporting_label_helper(
            self.descriptor, self.attr
        )


class CGSpecializedForwardingSetter(CGSpecializedSetter):
    """
    A class for generating the code for a specialized attribute setter with
    PutForwards that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        CGSpecializedSetter.__init__(self, descriptor, attr)

    def definition_body(self):
        attrName = self.attr.identifier.name
        forwardToAttrName = self.attr.getExtendedAttribute("PutForwards")[0]
        # JS_GetProperty and JS_SetProperty can only deal with ASCII
        assert all(ord(c) < 128 for c in attrName)
        assert all(ord(c) < 128 for c in forwardToAttrName)
        return fill(
            """
            JS::Rooted<JS::Value> v(cx);
            if (!JS_GetProperty(cx, obj, "${attr}", &v)) {
              return false;
            }

            if (!v.isObject()) {
              return cx.ThrowErrorMessage<MSG_NOT_OBJECT>("${interface}.${attr}");
            }

            JS::Rooted<JSObject*> targetObj(cx, &v.toObject());
            return JS_SetProperty(cx, targetObj, "${forwardToAttrName}", args[0]);
            """,
            attr=attrName,
            interface=self.descriptor.interface.identifier.name,
            forwardToAttrName=forwardToAttrName,
        )

    def error_reporting_label(self):
        # We always need to be able to throw.
        return '"%s"' % (
            GetLabelForErrorReporting(self.descriptor, self.attr, isConstructor=False)
            + " setter"
        )


class CGSpecializedReplaceableSetter(CGSpecializedSetter):
    """
    A class for generating the code for a specialized attribute setter with
    Replaceable that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        CGSpecializedSetter.__init__(self, descriptor, attr)

    def definition_body(self):
        attrName = self.attr.identifier.name
        # JS_DefineProperty can only deal with ASCII
        assert all(ord(c) < 128 for c in attrName)
        return (
            'return JS_DefineProperty(cx, obj, "%s", args[0], JSPROP_ENUMERATE);\n'
            % attrName
        )

    def error_reporting_label(self):
        # We never throw directly.
        return None


class CGSpecializedLenientSetter(CGSpecializedSetter):
    """
    A class for generating the code for a specialized attribute setter with
    LenientSetter that the JIT can call with lower overhead.
    """

    def __init__(self, descriptor, attr):
        CGSpecializedSetter.__init__(self, descriptor, attr)

    def definition_body(self):
        attrName = self.attr.identifier.name
        # JS_DefineProperty can only deal with ASCII
        assert all(ord(c) < 128 for c in attrName)
        return dedent(
            """
            DeprecationWarning(cx, obj, DeprecatedOperations::eLenientSetter);
            return true;
            """
        )

    def error_reporting_label(self):
        # We never throw; that's the whole point.
        return None


def memberReturnsNewObject(member):
    return member.getExtendedAttribute("NewObject") is not None


class CGMemberJITInfo(CGThing):
    """
    A class for generating the JITInfo for a property that points to
    our specialized getter and setter.
    """

    def __init__(self, descriptor, member):
        self.member = member
        self.descriptor = descriptor

    def declare(self):
        return ""

    def defineJitInfo(
        self,
        infoName,
        opName,
        opType,
        infallible,
        movable,
        eliminatable,
        aliasSet,
        alwaysInSlot,
        lazilyInSlot,
        slotIndex,
        returnTypes,
        args,
    ):
        """
        aliasSet is a JSJitInfo::AliasSet value, without the "JSJitInfo::" bit.

        args is None if we don't want to output argTypes for some
        reason (e.g. we have overloads or we're not a method) and
        otherwise an iterable of the arguments for this method.
        """
        assert (
            not movable or aliasSet != "AliasEverything"
        )  # Can't move write-aliasing things
        assert (
            not alwaysInSlot or movable
        )  # Things always in slots had better be movable
        assert (
            not eliminatable or aliasSet != "AliasEverything"
        )  # Can't eliminate write-aliasing things
        assert (
            not alwaysInSlot or eliminatable
        )  # Things always in slots had better be eliminatable

        def jitInfoInitializer(isTypedMethod):
            initializer = fill(
                """
                {
                  { ${opName} },
                  { prototypes::id::${name} },
                  { PrototypeTraits<prototypes::id::${name}>::Depth },
                  JSJitInfo::${opType},
                  JSJitInfo::${aliasSet}, /* aliasSet.  Not relevant for setters. */
                  ${returnType},  /* returnType.  Not relevant for setters. */
                  ${isInfallible},  /* isInfallible. False in setters. */
                  ${isMovable},  /* isMovable.  Not relevant for setters. */
                  ${isEliminatable}, /* isEliminatable.  Not relevant for setters. */
                  ${isAlwaysInSlot}, /* isAlwaysInSlot.  Only relevant for getters. */
                  ${isLazilyCachedInSlot}, /* isLazilyCachedInSlot.  Only relevant for getters. */
                  ${isTypedMethod},  /* isTypedMethod.  Only relevant for methods. */
                  ${slotIndex}   /* Reserved slot index, if we're stored in a slot, else 0. */
                }
                """,
                opName=opName,
                name=self.descriptor.name,
                opType=opType,
                aliasSet=aliasSet,
                returnType=functools.reduce(
                    CGMemberJITInfo.getSingleReturnType, returnTypes, ""
                ),
                isInfallible=toStringBool(infallible),
                isMovable=toStringBool(movable),
                isEliminatable=toStringBool(eliminatable),
                isAlwaysInSlot=toStringBool(alwaysInSlot),
                isLazilyCachedInSlot=toStringBool(lazilyInSlot),
                isTypedMethod=toStringBool(isTypedMethod),
                slotIndex="0" if slotIndex is None else slotIndex,
            )
            return initializer.rstrip()

        if slotIndex is not None:
            slotAssert = fill(
                """
                static_assert(${slotIndex} <= JSJitInfo::maxSlotIndex, "We won't fit");
                static_assert(${slotIndex} < ${classReservedSlots}, "There is no slot for us");
                """,
                slotIndex=slotIndex,
                classReservedSlots=INSTANCE_RESERVED_SLOTS
                + self.descriptor.interface.totalMembersInSlots,
            )
        else:
            slotAssert = ""
        if args is not None:
            argTypes = "%s_argTypes" % infoName
            args = [CGMemberJITInfo.getJSArgType(arg.type) for arg in args]
            args.append("JSJitInfo::ArgTypeListEnd")
            argTypesDecl = "static const JSJitInfo::ArgType %s[] = { %s };\n" % (
                argTypes,
                ", ".join(args),
            )
            return fill(
                """
                $*{argTypesDecl}
                static const JSTypedMethodJitInfo ${infoName} = {
                ${jitInfo},
                  ${argTypes}
                };
                $*{slotAssert}
                """,
                argTypesDecl=argTypesDecl,
                infoName=infoName,
                jitInfo=indent(jitInfoInitializer(True)),
                argTypes=argTypes,
                slotAssert=slotAssert,
            )

        # Unexposed things are meant to be used from C++ directly, so we make
        # their jitinfo non-static.  That way C++ can get at it.
        if self.member.getExtendedAttribute("Unexposed"):
            storageClass = "extern"
        else:
            storageClass = "static"

        return fill(
            """
            ${storageClass} const JSJitInfo ${infoName} = ${jitInfo};
            $*{slotAssert}
            """,
            storageClass=storageClass,
            infoName=infoName,
            jitInfo=jitInfoInitializer(False),
            slotAssert=slotAssert,
        )

    def define(self):
        if self.member.isAttr():
            getterinfo = "%s_getterinfo" % IDLToCIdentifier(self.member.identifier.name)
            name = IDLToCIdentifier(self.member.identifier.name)
            if self.member.type.isPromise():
                name = CGGetterPromiseWrapper.makeName(name)
            getter = "get_%s" % name
            extendedAttrs = self.descriptor.getExtendedAttributes(
                self.member, getter=True
            )
            getterinfal = "needsErrorResult" not in extendedAttrs

            # At this point getterinfal is true if our getter either can't throw
            # at all, or can only throw OOM.  In both cases, it's safe to move,
            # or dead-code-eliminate, the getter, because throwing OOM is not
            # semantically meaningful, so code can't rely on it happening.  Note
            # that this makes the behavior consistent for OOM thrown from the
            # getter itself and OOM thrown from the to-JS conversion of the
            # return value (see the "canOOM" and "infallibleForMember" checks
            # below).
            movable = self.mayBeMovable() and getterinfal
            eliminatable = self.mayBeEliminatable() and getterinfal
            aliasSet = self.aliasSet()

            # Now we have to set getterinfal to whether we can _really_ ever
            # throw, from the point of view of the JS engine.
            getterinfal = (
                getterinfal
                and "canOOM" not in extendedAttrs
                and infallibleForMember(self.member, self.member.type, self.descriptor)
            )
            isAlwaysInSlot = self.member.getExtendedAttribute("StoreInSlot")

            if self.member.slotIndices is not None:
                assert (
                    isAlwaysInSlot
                    or self.member.getExtendedAttribute("Cached")
                    or self.member.getExtendedAttribute(
                        "ReflectedHTMLAttributeReturningFrozenArray"
                    )
                    or self.member.type.isObservableArray()
                )
                isLazilyCachedInSlot = (
                    not isAlwaysInSlot
                    and not self.member.getExtendedAttribute(
                        "ReflectedHTMLAttributeReturningFrozenArray"
                    )
                )
                slotIndex = memberReservedSlot(self.member, self.descriptor)
                # We'll statically assert that this is not too big in
                # CGUpdateMemberSlotsMethod, in the case when
                # isAlwaysInSlot is true.
            else:
                isLazilyCachedInSlot = False
                slotIndex = None

            result = self.defineJitInfo(
                getterinfo,
                getter,
                "Getter",
                getterinfal,
                movable,
                eliminatable,
                aliasSet,
                isAlwaysInSlot,
                isLazilyCachedInSlot,
                slotIndex,
                [self.member.type],
                None,
            )
            if (
                not self.member.readonly
                or self.member.getExtendedAttribute("PutForwards") is not None
                or self.member.getExtendedAttribute("Replaceable") is not None
                or self.member.getExtendedAttribute("LegacyLenientSetter") is not None
            ):
                setterinfo = "%s_setterinfo" % IDLToCIdentifier(
                    self.member.identifier.name
                )
                # Actually a JSJitSetterOp, but JSJitGetterOp is first in the
                # union.
                setter = "(JSJitGetterOp)set_%s" % IDLToCIdentifier(
                    self.member.identifier.name
                )
                # Setters are always fallible, since they have to do a typed unwrap.
                result += self.defineJitInfo(
                    setterinfo,
                    setter,
                    "Setter",
                    False,
                    False,
                    False,
                    "AliasEverything",
                    False,
                    False,
                    None,
                    [BuiltinTypes[IDLBuiltinType.Types.undefined]],
                    None,
                )
            return result
        if self.member.isMethod():
            methodinfo = "%s_methodinfo" % IDLToCIdentifier(self.member.identifier.name)
            name = CppKeywords.checkMethodName(
                IDLToCIdentifier(self.member.identifier.name)
            )
            if self.member.returnsPromise():
                name = CGMethodPromiseWrapper.makeName(name)
            # Actually a JSJitMethodOp, but JSJitGetterOp is first in the union.
            method = "(JSJitGetterOp)%s" % name

            # Methods are infallible if they are infallible, have no arguments
            # to unwrap, and have a return type that's infallible to wrap up for
            # return.
            sigs = self.member.signatures()
            if len(sigs) != 1:
                # Don't handle overloading.  If there's more than one signature,
                # one of them must take arguments.
                methodInfal = False
                args = None
                movable = False
                eliminatable = False
            else:
                sig = sigs[0]
                # For methods that affect nothing, it's OK to set movable to our
                # notion of infallible on the C++ side, without considering
                # argument conversions, since argument conversions that can
                # reliably throw would be effectful anyway and the jit doesn't
                # move effectful things.
                extendedAttrs = self.descriptor.getExtendedAttributes(self.member)
                hasInfallibleImpl = "needsErrorResult" not in extendedAttrs
                # At this point hasInfallibleImpl is true if our method either
                # can't throw at all, or can only throw OOM.  In both cases, it
                # may be safe to move, or dead-code-eliminate, the method,
                # because throwing OOM is not semantically meaningful, so code
                # can't rely on it happening.  Note that this makes the behavior
                # consistent for OOM thrown from the method itself and OOM
                # thrown from the to-JS conversion of the return value (see the
                # "canOOM" and "infallibleForMember" checks below).
                movable = self.mayBeMovable() and hasInfallibleImpl
                eliminatable = self.mayBeEliminatable() and hasInfallibleImpl
                # XXXbz can we move the smarts about fallibility due to arg
                # conversions into the JIT, using our new args stuff?
                if len(sig[1]) != 0 or not infallibleForMember(
                    self.member, sig[0], self.descriptor
                ):
                    # We have arguments or our return-value boxing can fail
                    methodInfal = False
                else:
                    methodInfal = hasInfallibleImpl and "canOOM" not in extendedAttrs
                # For now, only bother to output args if we're side-effect-free.
                if self.member.affects == "Nothing":
                    args = sig[1]
                else:
                    args = None

            aliasSet = self.aliasSet()
            result = self.defineJitInfo(
                methodinfo,
                method,
                "Method",
                methodInfal,
                movable,
                eliminatable,
                aliasSet,
                False,
                False,
                None,
                [s[0] for s in sigs],
                args,
            )
            return result
        raise TypeError("Illegal member type to CGPropertyJITInfo")

    def mayBeMovable(self):
        """
        Returns whether this attribute or method may be movable, just
        based on Affects/DependsOn annotations.
        """
        affects = self.member.affects
        dependsOn = self.member.dependsOn
        assert affects in IDLInterfaceMember.AffectsValues
        assert dependsOn in IDLInterfaceMember.DependsOnValues
        # Things that are DependsOn=DeviceState are not movable, because we
        # don't want them coalesced with each other or loop-hoisted, since
        # their return value can change even if nothing is going on from our
        # point of view.
        return affects == "Nothing" and (
            dependsOn != "Everything" and dependsOn != "DeviceState"
        )

    def mayBeEliminatable(self):
        """
        Returns whether this attribute or method may be eliminatable, just
        based on Affects/DependsOn annotations.
        """
        # dependsOn shouldn't affect this decision at all, except in jitinfo we
        # have no way to express "Depends on everything, affects nothing",
        # because we only have three alias set values: AliasNone ("depends on
        # nothing, affects nothing"), AliasDOMSets ("depends on DOM sets,
        # affects nothing"), AliasEverything ("depends on everything, affects
        # everything").  So the [Affects=Nothing, DependsOn=Everything] case
        # gets encoded as AliasEverything and defineJitInfo asserts that if our
        # alias state is AliasEverything then we're not eliminatable (because it
        # thinks we might have side-effects at that point).  Bug 1155796 is
        # tracking possible solutions for this.
        affects = self.member.affects
        dependsOn = self.member.dependsOn
        assert affects in IDLInterfaceMember.AffectsValues
        assert dependsOn in IDLInterfaceMember.DependsOnValues
        return affects == "Nothing" and dependsOn != "Everything"

    def aliasSet(self):
        """
        Returns the alias set to store in the jitinfo.  This may not be the
        effective alias set the JIT uses, depending on whether we have enough
        information about our args to allow the JIT to prove that effectful
        argument conversions won't happen.
        """
        dependsOn = self.member.dependsOn
        assert dependsOn in IDLInterfaceMember.DependsOnValues

        if dependsOn == "Nothing" or dependsOn == "DeviceState":
            assert self.member.affects == "Nothing"
            return "AliasNone"

        if dependsOn == "DOMState":
            assert self.member.affects == "Nothing"
            return "AliasDOMSets"

        return "AliasEverything"

    @staticmethod
    def getJSReturnTypeTag(t):
        if t.nullable():
            # Sometimes it might return null, sometimes not
            return "JSVAL_TYPE_UNKNOWN"
        if t.isUndefined():
            # No return, every time
            return "JSVAL_TYPE_UNDEFINED"
        if t.isSequence():
            return "JSVAL_TYPE_OBJECT"
        if t.isRecord():
            return "JSVAL_TYPE_OBJECT"
        if t.isPromise():
            return "JSVAL_TYPE_OBJECT"
        if t.isGeckoInterface():
            return "JSVAL_TYPE_OBJECT"
        if t.isString():
            return "JSVAL_TYPE_STRING"
        if t.isEnum():
            return "JSVAL_TYPE_STRING"
        if t.isCallback():
            return "JSVAL_TYPE_OBJECT"
        if t.isAny():
            # The whole point is to return various stuff
            return "JSVAL_TYPE_UNKNOWN"
        if t.isObject():
            return "JSVAL_TYPE_OBJECT"
        if t.isSpiderMonkeyInterface():
            return "JSVAL_TYPE_OBJECT"
        if t.isUnion():
            u = t.unroll()
            if u.hasNullableType:
                # Might be null or not
                return "JSVAL_TYPE_UNKNOWN"
            return functools.reduce(
                CGMemberJITInfo.getSingleReturnType, u.flatMemberTypes, ""
            )
        if t.isDictionary():
            return "JSVAL_TYPE_OBJECT"
        if t.isObservableArray():
            return "JSVAL_TYPE_OBJECT"
        if not t.isPrimitive():
            raise TypeError("No idea what type " + str(t) + " is.")
        tag = t.tag()
        if tag == IDLType.Tags.bool:
            return "JSVAL_TYPE_BOOLEAN"
        if tag in [
            IDLType.Tags.int8,
            IDLType.Tags.uint8,
            IDLType.Tags.int16,
            IDLType.Tags.uint16,
            IDLType.Tags.int32,
        ]:
            return "JSVAL_TYPE_INT32"
        if tag in [
            IDLType.Tags.int64,
            IDLType.Tags.uint64,
            IDLType.Tags.unrestricted_float,
            IDLType.Tags.float,
            IDLType.Tags.unrestricted_double,
            IDLType.Tags.double,
        ]:
            # These all use JS_NumberValue, which can return int or double.
            # But TI treats "double" as meaning "int or double", so we're
            # good to return JSVAL_TYPE_DOUBLE here.
            return "JSVAL_TYPE_DOUBLE"
        if tag != IDLType.Tags.uint32:
            raise TypeError("No idea what type " + str(t) + " is.")
        # uint32 is sometimes int and sometimes double.
        return "JSVAL_TYPE_DOUBLE"

    @staticmethod
    def getSingleReturnType(existingType, t):
        type = CGMemberJITInfo.getJSReturnTypeTag(t)
        if existingType == "":
            # First element of the list; just return its type
            return type

        if type == existingType:
            return existingType
        if (type == "JSVAL_TYPE_DOUBLE" and existingType == "JSVAL_TYPE_INT32") or (
            existingType == "JSVAL_TYPE_DOUBLE" and type == "JSVAL_TYPE_INT32"
        ):
            # Promote INT32 to DOUBLE as needed
            return "JSVAL_TYPE_DOUBLE"
        # Different types
        return "JSVAL_TYPE_UNKNOWN"

    @staticmethod
    def getJSArgType(t):
        assert not t.isUndefined()
        if t.nullable():
            # Sometimes it might return null, sometimes not
            return (
                "JSJitInfo::ArgType(JSJitInfo::Null | %s)"
                % CGMemberJITInfo.getJSArgType(t.inner)
            )
        if t.isSequence():
            return "JSJitInfo::Object"
        if t.isPromise():
            return "JSJitInfo::Object"
        if t.isGeckoInterface():
            return "JSJitInfo::Object"
        if t.isString():
            return "JSJitInfo::String"
        if t.isEnum():
            return "JSJitInfo::String"
        if t.isCallback():
            return "JSJitInfo::Object"
        if t.isAny():
            # The whole point is to return various stuff
            return "JSJitInfo::Any"
        if t.isObject():
            return "JSJitInfo::Object"
        if t.isSpiderMonkeyInterface():
            return "JSJitInfo::Object"
        if t.isUnion():
            u = t.unroll()
            type = "JSJitInfo::Null" if u.hasNullableType else ""
            return "JSJitInfo::ArgType(%s)" % functools.reduce(
                CGMemberJITInfo.getSingleArgType, u.flatMemberTypes, type
            )
        if t.isDictionary():
            return "JSJitInfo::Object"
        if not t.isPrimitive():
            raise TypeError("No idea what type " + str(t) + " is.")
        tag = t.tag()
        if tag == IDLType.Tags.bool:
            return "JSJitInfo::Boolean"
        if tag in [
            IDLType.Tags.int8,
            IDLType.Tags.uint8,
            IDLType.Tags.int16,
            IDLType.Tags.uint16,
            IDLType.Tags.int32,
        ]:
            return "JSJitInfo::Integer"
        if tag in [
            IDLType.Tags.int64,
            IDLType.Tags.uint64,
            IDLType.Tags.unrestricted_float,
            IDLType.Tags.float,
            IDLType.Tags.unrestricted_double,
            IDLType.Tags.double,
        ]:
            # These all use JS_NumberValue, which can return int or double.
            # But TI treats "double" as meaning "int or double", so we're
            # good to return JSVAL_TYPE_DOUBLE here.
            return "JSJitInfo::Double"
        if tag != IDLType.Tags.uint32:
            raise TypeError("No idea what type " + str(t) + " is.")
        # uint32 is sometimes int and sometimes double.
        return "JSJitInfo::Double"

    @staticmethod
    def getSingleArgType(existingType, t):
        type = CGMemberJITInfo.getJSArgType(t)
        if existingType == "":
            # First element of the list; just return its type
            return type

        if type == existingType:
            return existingType
        return "%s | %s" % (existingType, type)


class CGStaticMethodJitinfo(CGGeneric):
    """
    A class for generating the JITInfo for a promise-returning static method.
    """

    def __init__(self, method):
        CGGeneric.__init__(
            self,
            "\n"
            "static const JSJitInfo %s_methodinfo = {\n"
            "  { (JSJitGetterOp)%s },\n"
            "  { prototypes::id::_ID_Count }, { 0 }, JSJitInfo::StaticMethod,\n"
            "  JSJitInfo::AliasEverything, JSVAL_TYPE_OBJECT, false, false,\n"
            "  false, false, 0\n"
            "};\n"
            % (
                IDLToCIdentifier(method.identifier.name),
                CppKeywords.checkMethodName(IDLToCIdentifier(method.identifier.name)),
            ),
        )


def getEnumValueName(value):
    # Some enum values can be empty strings.  Others might have weird
    # characters in them.  Deal with the former by returning "_empty",
    # deal with possible name collisions from that by throwing if the
    # enum value is actually "_empty", and throw on any value
    # containing non-ASCII chars for now. Replace all chars other than
    # [0-9A-Za-z_] with '_'.
    if re.match("[^\x20-\x7E]", value):
        raise SyntaxError('Enum value "' + value + '" contains non-ASCII characters')
    if re.match("^[0-9]", value):
        value = "_" + value
    value = re.sub(r"[^0-9A-Za-z_]", "_", value)
    if re.match("^_[A-Z]|__", value):
        raise SyntaxError('Enum value "' + value + '" is reserved by the C++ spec')
    if value == "_empty":
        raise SyntaxError('"_empty" is not an IDL enum value we support yet')
    if value == "":
        return "_empty"
    return MakeNativeName(value)


class CGEnumToJSValue(CGAbstractMethod):
    def __init__(self, enum):
        enumType = enum.identifier.name
        self.stringsArray = "binding_detail::EnumStrings<" + enumType + ">::Values"
        CGAbstractMethod.__init__(
            self,
            None,
            "ToJSValue",
            "bool",
            [
                Argument("JSContext*", "aCx"),
                Argument(enumType, "aArgument"),
                Argument("JS::MutableHandle<JS::Value>", "aValue"),
            ],
        )

    def definition_body(self):
        return fill(
            """
            MOZ_ASSERT(uint32_t(aArgument) < std::size(${strings}));
            JSString* resultStr =
              JS_NewStringCopyN(aCx, ${strings}[uint32_t(aArgument)].BeginReading(),
                                ${strings}[uint32_t(aArgument)].Length());
            if (!resultStr) {
              return false;
            }
            aValue.setString(resultStr);
            return true;
            """,
            strings=self.stringsArray,
        )


class CGEnum(CGThing):
    def __init__(self, enum):
        CGThing.__init__(self)
        self.enum = enum
        strings = CGNamespace(
            "binding_detail",
            CGGeneric(
                declare=fill(
                    """
                    template <> struct EnumStrings<${name}> {
                      static constexpr nsLiteralCString Values[${count}] {
                        $*{entries}
                      };
                    };
                    """,
                    name=self.enum.identifier.name,
                    count=self.nEnumStrings(),
                    entries="".join('"%s"_ns,\n' % val for val in self.enum.values()),
                ),
                define=fill(
                    """
                    constexpr nsLiteralCString EnumStrings<${name}>::Values[${count}];
                    """,
                    name=self.enum.identifier.name,
                    count=self.nEnumStrings(),
                ),
            ),
        )
        toJSValue = CGEnumToJSValue(enum)
        self.cgThings = CGList([strings, toJSValue], "\n")

    def nEnumStrings(self):
        return len(self.enum.values())

    @staticmethod
    def underlyingType(enum):
        count = len(enum.values())
        if count <= 256:
            return "uint8_t"
        if count <= 65536:
            return "uint16_t"
        raise ValueError("Enum " + enum.identifier.name + " has more than 65536 values")

    def declare(self):
        decl = fill(
            """
            enum class ${name} : ${ty} {
              $*{enums}
            };
            """,
            name=self.enum.identifier.name,
            ty=CGEnum.underlyingType(self.enum),
            enums=",\n".join(map(getEnumValueName, self.enum.values())) + ",\n",
        )

        return decl + "\n" + self.cgThings.declare()

    def define(self):
        return self.cgThings.define()

    def deps(self):
        return self.enum.getDeps()


class CGMaxContiguousEnumValue(CGThing):
    def __init__(self, enum):
        CGThing.__init__(self)
        self.enum = enum

    def declare(self):
        enumValues = self.enum.values()
        return fill(
            """
            template <>
            struct MaxContiguousEnumValue<dom::${name}>
            {
              static constexpr dom::${name} value = dom::${name}::${maxValue};

              static_assert(static_cast<${ty}>(dom::${name}::${minValue}) == 0,
                            "We rely on this in ContiguousEnumValues");
              static_assert(std::size(dom::binding_detail::EnumStrings<dom::${name}>::Values) - 1 == UnderlyingValue(value),
                            "Mismatch between enum strings and enum count");
            };
            """,
            name=self.enum.identifier.name,
            ty=CGEnum.underlyingType(self.enum),
            maxValue=getEnumValueName(enumValues[-1]),
            minValue=getEnumValueName(enumValues[0]),
        )

    def define(self):
        return ""

    def deps(self):
        return self.enum.getDeps()


def getUnionAccessorSignatureType(type, descriptorProvider):
    """
    Returns the types that are used in the getter and setter signatures for
    union types
    """
    # Flat member types have already unwrapped nullables.
    assert not type.nullable()

    # Promise types can never appear in unions, because Promise is not
    # distinguishable from anything.
    assert not type.isPromise()

    if type.isSequence() or type.isRecord():
        if type.isSequence():
            wrapperType = "Sequence"
        else:
            wrapperType = "Record"
        # We don't use the returned template here, so it's OK to just pass no
        # sourceDescription.
        elementInfo = getJSToNativeConversionInfo(
            type.inner, descriptorProvider, isMember=wrapperType
        )
        if wrapperType == "Sequence":
            innerType = elementInfo.declType
        else:
            innerType = [recordKeyDeclType(type), elementInfo.declType]

        return CGTemplatedType(wrapperType, innerType, isConst=True, isReference=True)

    # Nested unions are unwrapped automatically into our flatMemberTypes.
    assert not type.isUnion()

    if type.isGeckoInterface():
        descriptor = descriptorProvider.getDescriptor(
            type.unroll().inner.identifier.name
        )
        typeName = CGGeneric(descriptor.nativeType)
        if not type.unroll().inner.isExternal():
            typeName = CGWrapper(typeName, post="&")
        elif descriptor.interface.identifier.name == "WindowProxy":
            typeName = CGGeneric("WindowProxyHolder const&")
        else:
            # Allow null pointers for old-binding classes.
            typeName = CGWrapper(typeName, post="*")
        return typeName

    if type.isSpiderMonkeyInterface():
        typeName = CGGeneric(type.name)
        return CGWrapper(typeName, post=" const &")

    if type.isJSString():
        raise TypeError("JSString not supported in unions")

    if type.isDOMString() or type.isUSVString():
        return CGGeneric("const nsAString&")

    if type.isUTF8String():
        return CGGeneric("const nsACString&")

    if type.isByteString():
        return CGGeneric("const nsCString&")

    if type.isEnum():
        return CGGeneric(type.inner.identifier.name)

    if type.isCallback():
        return CGGeneric("%s&" % type.unroll().callback.identifier.name)

    if type.isAny():
        return CGGeneric("JS::Value")

    if type.isObject():
        return CGGeneric("JSObject*")

    if type.isDictionary():
        return CGGeneric("const %s&" % type.inner.identifier.name)

    if not type.isPrimitive():
        raise TypeError("Need native type for argument type '%s'" % str(type))

    return CGGeneric(builtinNames[type.tag()])


def getUnionTypeTemplateVars(unionType, type, descriptorProvider, isMember=False):
    assert not type.isUndefined()
    assert not isMember or isMember in ("Union", "OwningUnion")

    ownsMembers = isMember == "OwningUnion"
    name = getUnionMemberName(type)
    holderName = "m" + name + "Holder"

    # By the time tryNextCode is invoked, we're guaranteed the union has been
    # constructed as some type, since we've been trying to convert into the
    # corresponding member.
    tryNextCode = fill(
        """
        Destroy${name}();
        tryNext = true;
        return true;
        """,
        name=name,
    )

    sourceDescription = "%s branch of %s" % (type.prettyName(), unionType.prettyName())

    conversionInfo = getJSToNativeConversionInfo(
        type,
        descriptorProvider,
        failureCode=tryNextCode,
        isDefinitelyObject=not type.isDictionary(),
        isMember=isMember,
        sourceDescription=sourceDescription,
    )

    ctorNeedsCx = conversionInfo.declArgs == "cx"
    ctorArgs = "cx" if ctorNeedsCx else ""

    structType = conversionInfo.declType.define()
    externalType = getUnionAccessorSignatureType(type, descriptorProvider).define()

    if type.isObject():
        if ownsMembers:
            setValue = "mValue.mObject.SetValue(obj);"
        else:
            setValue = "mValue.mObject.SetValue(cx, obj);"

        body = fill(
            """
            MOZ_ASSERT(mType == eUninitialized);
            ${setValue}
            mType = eObject;
            """,
            setValue=setValue,
        )

        # It's a bit sketchy to do the security check after setting the value,
        # but it keeps the code cleaner and lets us avoid rooting |obj| over the
        # call to CallerSubsumes().
        body = body + fill(
            """
            if (passedToJSImpl && !CallerSubsumes(obj)) {
              cx.ThrowErrorMessage<MSG_PERMISSION_DENIED_TO_PASS_ARG>("${sourceDescription}");
              return false;
            }
            return true;
            """,
            sourceDescription=sourceDescription,
        )

        setters = [
            ClassMethod(
                "SetToObject",
                "bool",
                [
                    Argument("BindingCallContext&", "cx"),
                    Argument("JSObject*", "obj"),
                    Argument("bool", "passedToJSImpl", default="false"),
                ],
                inline=True,
                bodyInHeader=True,
                body=body,
            )
        ]
    elif type.isDictionary() and not type.inner.needsConversionFromJS:
        # In this case we are never initialized from JS to start with
        setters = None
    else:
        # Important: we need to not have our declName involve
        # maybe-GCing operations.
        jsConversion = fill(
            conversionInfo.template,
            val="value",
            maybeMutableVal="value",
            declName="memberSlot",
            holderName=(holderName if ownsMembers else "%s.ref()" % holderName),
            passedToJSImpl="passedToJSImpl",
        )

        jsConversion = fill(
            """
            tryNext = false;
            { // scope for memberSlot
              ${structType}& memberSlot = RawSetAs${name}(${ctorArgs});
              $*{jsConversion}
            }
            return true;
            """,
            structType=structType,
            name=name,
            ctorArgs=ctorArgs,
            jsConversion=jsConversion,
        )

        needCallContext = idlTypeNeedsCallContext(type)
        if needCallContext:
            cxType = "BindingCallContext&"
        else:
            cxType = "JSContext*"
        setters = [
            ClassMethod(
                "TrySetTo" + name,
                "bool",
                [
                    Argument(cxType, "cx"),
                    Argument("JS::Handle<JS::Value>", "value"),
                    Argument("bool&", "tryNext"),
                    Argument("bool", "passedToJSImpl", default="false"),
                ],
                visibility="private",
                body=jsConversion,
            )
        ]
        if needCallContext:
            # Add a method for non-binding uses of unions to allow them to set
            # things in the union without providing a call context (though if
            # they want good error reporting they'll provide one anyway).
            shimBody = fill(
                """
                BindingCallContext cx(cx_, nullptr);
                return TrySetTo${name}(cx, value, tryNext, passedToJSImpl);
                """,
                name=name,
            )
            setters.append(
                ClassMethod(
                    "TrySetTo" + name,
                    "bool",
                    [
                        Argument("JSContext*", "cx_"),
                        Argument("JS::Handle<JS::Value>", "value"),
                        Argument("bool&", "tryNext"),
                        Argument("bool", "passedToJSImpl", default="false"),
                    ],
                    visibility="private",
                    body=shimBody,
                )
            )

    return {
        "name": name,
        "structType": structType,
        "externalType": externalType,
        "setters": setters,
        "ctorArgs": ctorArgs,
        "ctorArgList": [Argument("JSContext*", "cx")] if ctorNeedsCx else [],
    }


def getUnionConversionTemplate(type):
    assert type.isUnion()
    assert not type.nullable()

    memberTypes = type.flatMemberTypes
    prettyNames = []

    interfaceMemberTypes = [t for t in memberTypes if t.isNonCallbackInterface()]
    if len(interfaceMemberTypes) > 0:
        interfaceObject = []
        for memberType in interfaceMemberTypes:
            name = getUnionMemberName(memberType)
            interfaceObject.append(
                CGGeneric(
                    "(failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext"
                    % name
                )
            )
            prettyNames.append(memberType.prettyName())
        interfaceObject = CGWrapper(
            CGList(interfaceObject, " ||\n"),
            pre="done = ",
            post=";\n",
            reindent=True,
        )
    else:
        interfaceObject = None

    sequenceObjectMemberTypes = [t for t in memberTypes if t.isSequence()]
    if len(sequenceObjectMemberTypes) > 0:
        assert len(sequenceObjectMemberTypes) == 1
        memberType = sequenceObjectMemberTypes[0]
        name = getUnionMemberName(memberType)
        sequenceObject = CGGeneric(
            "done = (failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n"
            % name
        )
        prettyNames.append(memberType.prettyName())
    else:
        sequenceObject = None

    callbackMemberTypes = [
        t for t in memberTypes if t.isCallback() or t.isCallbackInterface()
    ]
    if len(callbackMemberTypes) > 0:
        assert len(callbackMemberTypes) == 1
        memberType = callbackMemberTypes[0]
        name = getUnionMemberName(memberType)
        callbackObject = CGGeneric(
            "done = (failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n"
            % name
        )
        prettyNames.append(memberType.prettyName())
    else:
        callbackObject = None

    dictionaryMemberTypes = [t for t in memberTypes if t.isDictionary()]
    if len(dictionaryMemberTypes) > 0:
        assert len(dictionaryMemberTypes) == 1
        memberType = dictionaryMemberTypes[0]
        name = getUnionMemberName(memberType)
        setDictionary = CGGeneric(
            "done = (failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n"
            % name
        )
        prettyNames.append(memberType.prettyName())
    else:
        setDictionary = None

    recordMemberTypes = [t for t in memberTypes if t.isRecord()]
    if len(recordMemberTypes) > 0:
        assert len(recordMemberTypes) == 1
        memberType = recordMemberTypes[0]
        name = getUnionMemberName(memberType)
        recordObject = CGGeneric(
            "done = (failed = !TrySetTo%s(cx, ${val}, tryNext, ${passedToJSImpl})) || !tryNext;\n"
            % name
        )
        prettyNames.append(memberType.prettyName())
    else:
        recordObject = None

    objectMemberTypes = [t for t in memberTypes if t.isObject()]
    if len(objectMemberTypes) > 0:
        assert len(objectMemberTypes) == 1
        # Very important to NOT construct a temporary Rooted here, since the
        # SetToObject call can call a Rooted constructor and we need to keep
        # stack discipline for Rooted.
        object = CGGeneric(
            "if (!SetToObject(cx, &${val}.toObject(), ${passedToJSImpl})) {\n"
            "  return false;\n"
            "}\n"
            "done = true;\n"
        )
        prettyNames.append(objectMemberTypes[0].prettyName())
    else:
        object = None

    hasObjectTypes = (
        interfaceObject or sequenceObject or callbackObject or object or recordObject
    )
    if hasObjectTypes:
        # "object" is not distinguishable from other types
        assert not object or not (
            interfaceObject or sequenceObject or callbackObject or recordObject
        )
        if sequenceObject or callbackObject:
            # An object can be both an sequence object and a callback or
            # dictionary, but we shouldn't have both in the union's members
            # because they are not distinguishable.
            assert not (sequenceObject and callbackObject)
            templateBody = CGElseChain([sequenceObject, callbackObject])
        else:
            templateBody = None
        if interfaceObject:
            assert not object
            if templateBody:
                templateBody = CGIfWrapper(templateBody, "!done")
            templateBody = CGList([interfaceObject, templateBody])
        else:
            templateBody = CGList([templateBody, object])

        if recordObject:
            templateBody = CGList([templateBody, CGIfWrapper(recordObject, "!done")])

        templateBody = CGIfWrapper(templateBody, "${val}.isObject()")
    else:
        templateBody = CGGeneric()

    if setDictionary:
        assert not object
        templateBody = CGList([templateBody, CGIfWrapper(setDictionary, "!done")])

    stringTypes = [t for t in memberTypes if t.isString() or t.isEnum()]
    numericTypes = [t for t in memberTypes if t.isNumeric()]
    booleanTypes = [t for t in memberTypes if t.isBoolean()]
    if stringTypes or numericTypes or booleanTypes:
        assert len(stringTypes) <= 1
        assert len(numericTypes) <= 1
        assert len(booleanTypes) <= 1

        # We will wrap all this stuff in a do { } while (0); so we
        # can use "break" for flow control.
        def getStringOrPrimitiveConversion(memberType):
            name = getUnionMemberName(memberType)
            return CGGeneric(
                "done = (failed = !TrySetTo%s(cx, ${val}, tryNext)) || !tryNext;\n"
                "break;\n" % name
            )

        other = CGList([])
        stringConversion = [getStringOrPrimitiveConversion(t) for t in stringTypes]
        numericConversion = [getStringOrPrimitiveConversion(t) for t in numericTypes]
        booleanConversion = [getStringOrPrimitiveConversion(t) for t in booleanTypes]
        if stringConversion:
            if booleanConversion:
                other.append(CGIfWrapper(booleanConversion[0], "${val}.isBoolean()"))
            if numericConversion:
                other.append(CGIfWrapper(numericConversion[0], "${val}.isNumber()"))
            other.append(stringConversion[0])
        elif numericConversion:
            if booleanConversion:
                other.append(CGIfWrapper(booleanConversion[0], "${val}.isBoolean()"))
            other.append(numericConversion[0])
        else:
            assert booleanConversion
            other.append(booleanConversion[0])

        other = CGWrapper(CGIndenter(other), pre="do {\n", post="} while (false);\n")
        if hasObjectTypes or setDictionary:
            other = CGWrapper(CGIndenter(other), "{\n", post="}\n")
            if object:
                templateBody = CGElseChain([templateBody, other])
            else:
                other = CGWrapper(other, pre="if (!done) ")
                templateBody = CGList([templateBody, other])
        else:
            assert templateBody.define() == ""
            templateBody = other
    else:
        other = None

    templateBody = CGWrapper(
        templateBody, pre="bool done = false, failed = false, tryNext;\n"
    )
    throw = CGGeneric(
        fill(
            """
            if (failed) {
              return false;
            }
            if (!done) {
              cx.ThrowErrorMessage<MSG_NOT_IN_UNION>(sourceDescription, "${names}");
              return false;
            }
            """,
            names=", ".join(prettyNames),
        )
    )

    templateBody = CGList([templateBody, throw])

    hasUndefinedType = any(t.isUndefined() for t in memberTypes)
    elseChain = []

    # The spec does this before anything else, but we do it after checking
    # for null in the case of a nullable union. In practice this shouldn't
    # make a difference, but it makes things easier because we first need to
    # call Construct on our Maybe<...>, before we can set the union type to
    # undefined, and we do that below after checking for null (see the
    # 'if nullable:' block below).
    if hasUndefinedType:
        elseChain.append(
            CGIfWrapper(
                CGGeneric("SetUndefined();\n"),
                "${val}.isUndefined()",
            )
        )

    if type.hasNullableType:
        nullTest = (
            "${val}.isNull()" if hasUndefinedType else "${val}.isNullOrUndefined()"
        )
        elseChain.append(
            CGIfWrapper(
                CGGeneric("SetNull();\n"),
                nullTest,
            )
        )

    if len(elseChain) > 0:
        elseChain.append(CGWrapper(CGIndenter(templateBody), pre="{\n", post="}\n"))
        templateBody = CGElseChain(elseChain)

    return templateBody


def getUnionInitMethods(type, isOwningUnion=False):
    assert type.isUnion()

    template = getUnionConversionTemplate(type).define()

    replacements = {
        "val": "value",
        "passedToJSImpl": "passedToJSImpl",
    }

    initBody = fill(
        """
        MOZ_ASSERT(mType == eUninitialized);

        $*{conversion}
        return true;
        """,
        conversion=string.Template(template).substitute(replacements),
    )

    return [
        ClassMethod(
            "Init",
            "bool",
            [
                Argument("BindingCallContext&", "cx"),
                Argument("JS::Handle<JS::Value>", "value"),
                Argument("const char*", "sourceDescription", default='"Value"'),
                Argument("bool", "passedToJSImpl", default="false"),
            ],
            visibility="public",
            body=initBody,
        ),
        ClassMethod(
            "Init",
            "bool",
            [
                Argument("JSContext*", "cx_"),
                Argument("JS::Handle<JS::Value>", "value"),
                Argument("const char*", "sourceDescription", default='"Value"'),
                Argument("bool", "passedToJSImpl", default="false"),
            ],
            visibility="public",
            body=dedent(
                """
                BindingCallContext cx(cx_, nullptr);
                return Init(cx, value, sourceDescription, passedToJSImpl);
                """
            ),
        ),
    ]


class CGUnionStruct(CGThing):
    def __init__(self, type, descriptorProvider, ownsMembers=False):
        CGThing.__init__(self)
        self.type = type.unroll()
        self.descriptorProvider = descriptorProvider
        self.ownsMembers = ownsMembers
        self.struct = self.getStruct()

    def declare(self):
        return self.struct.declare()

    def define(self):
        return self.struct.define()

    def deps(self):
        return self.type.getDeps()

    def getStruct(self):
        members = [
            ClassMember("mType", "TypeOrUninit", body="eUninitialized"),
            ClassMember("mValue", "Value"),
        ]
        ctor = ClassConstructor(
            [], bodyInHeader=True, visibility="public", explicit=True
        )

        methods = []
        enumValues = ["eUninitialized"]
        toJSValCases = [
            CGCase(
                "eUninitialized", CGGeneric("return false;\n"), CGCase.DONT_ADD_BREAK
            )
        ]
        destructorCases = [CGCase("eUninitialized", None)]
        assignmentCase = CGCase(
            "eUninitialized",
            CGGeneric(
                "MOZ_ASSERT(mType == eUninitialized,\n"
                '           "We need to destroy ourselves?");\n'
            ),
        )
        assignmentCases = [assignmentCase]
        moveCases = [assignmentCase]
        traceCases = []
        unionValues = []

        def addSpecialType(typename):
            enumValue = "e" + typename
            enumValues.append(enumValue)
            methods.append(
                ClassMethod(
                    "Is" + typename,
                    "bool",
                    [],
                    const=True,
                    inline=True,
                    body="return mType == %s;\n" % enumValue,
                    bodyInHeader=True,
                )
            )
            methods.append(
                ClassMethod(
                    "Set" + typename,
                    "void",
                    [],
                    inline=True,
                    body=fill(
                        """
                        Uninit();
                        mType = ${enumValue};
                        """,
                        enumValue=enumValue,
                    ),
                    bodyInHeader=True,
                )
            )
            destructorCases.append(CGCase(enumValue, None))
            assignmentCase = CGCase(
                enumValue,
                CGGeneric(
                    fill(
                        """
                            MOZ_ASSERT(mType == eUninitialized);
                            mType = ${enumValue};
                            """,
                        enumValue=enumValue,
                    )
                ),
            )
            assignmentCases.append(assignmentCase)
            moveCases.append(assignmentCase)
            toJSValCases.append(
                CGCase(
                    enumValue,
                    CGGeneric(
                        fill(
                            """
                            rval.set${typename}();
                            return true;
                            """,
                            typename=typename,
                        )
                    ),
                    CGCase.DONT_ADD_BREAK,
                )
            )

        if self.type.hasNullableType:
            addSpecialType("Null")

        hasObjectType = any(t.isObject() for t in self.type.flatMemberTypes)
        skipToJSVal = False
        for t in self.type.flatMemberTypes:
            if t.isUndefined():
                addSpecialType("Undefined")
                continue

            vars = getUnionTypeTemplateVars(
                self.type,
                t,
                self.descriptorProvider,
                isMember="OwningUnion" if self.ownsMembers else "Union",
            )
            if vars["setters"]:
                methods.extend(vars["setters"])
            uninit = "Uninit();"
            if hasObjectType and not self.ownsMembers:
                uninit = (
                    'MOZ_ASSERT(mType != eObject, "This will not play well with Rooted");\n'
                    + uninit
                )
            if not t.isObject() or self.ownsMembers:
                body = fill(
                    """
                    if (mType == e${name}) {
                      return mValue.m${name}.Value();
                    }
                    %s
                    mType = e${name};
                    return mValue.m${name}.SetValue(${ctorArgs});
                    """,
                    **vars,
                )

                # bodyInHeader must be false for return values because they own
                # their union members and we don't want include headers in
                # UnionTypes.h just to call Addref/Release
                methods.append(
                    ClassMethod(
                        "RawSetAs" + vars["name"],
                        vars["structType"] + "&",
                        vars["ctorArgList"],
                        bodyInHeader=not self.ownsMembers,
                        body=body % "MOZ_ASSERT(mType == eUninitialized);",
                        noDiscard=True,
                    )
                )
                methods.append(
                    ClassMethod(
                        "SetAs" + vars["name"],
                        vars["structType"] + "&",
                        vars["ctorArgList"],
                        bodyInHeader=not self.ownsMembers,
                        body=body % uninit,
                        noDiscard=True,
                    )
                )

                # Provide a SetStringLiteral() method to support string defaults.
                if t.isByteString() or t.isUTF8String():
                    charType = "const nsCString::char_type"
                elif t.isString():
                    charType = "const nsString::char_type"
                else:
                    charType = None

                if charType:
                    methods.append(
                        ClassMethod(
                            "SetStringLiteral",
                            "void",
                            # Hack, but it works...
                            [Argument(charType, "(&aData)[N]")],
                            inline=True,
                            bodyInHeader=True,
                            templateArgs=["int N"],
                            body="RawSetAs%s().AssignLiteral(aData);\n" % t.name,
                        )
                    )

            body = fill("return mType == e${name};\n", **vars)
            methods.append(
                ClassMethod(
                    "Is" + vars["name"],
                    "bool",
                    [],
                    const=True,
                    bodyInHeader=True,
                    body=body,
                )
            )

            body = fill(
                """
                MOZ_RELEASE_ASSERT(Is${name}(), "Wrong type!");
                mValue.m${name}.Destroy();
                mType = eUninitialized;
                """,
                **vars,
            )
            methods.append(
                ClassMethod(
                    "Destroy" + vars["name"],
                    "void",
                    [],
                    visibility="private",
                    bodyInHeader=not self.ownsMembers,
                    body=body,
                )
            )

            body = fill(
                """
                MOZ_RELEASE_ASSERT(Is${name}(), "Wrong type!");
                return mValue.m${name}.Value();
                """,
                **vars,
            )
            # The non-const version of GetAs* returns our internal type
            getterReturnType = "%s&" % vars["structType"]
            methods.append(
                ClassMethod(
                    "GetAs" + vars["name"],
                    getterReturnType,
                    [],
                    bodyInHeader=True,
                    body=body,
                )
            )
            # The const version of GetAs* returns our internal type
            # for owning unions, but our external type for non-owning
            # ones.
            if self.ownsMembers:
                getterReturnType = "%s const &" % vars["structType"]
            else:
                getterReturnType = vars["externalType"]
            methods.append(
                ClassMethod(
                    "GetAs" + vars["name"],
                    getterReturnType,
                    [],
                    const=True,
                    bodyInHeader=True,
                    body=body,
                )
            )

            unionValues.append(fill("UnionMember<${structType} > m${name}", **vars))
            destructorCases.append(
                CGCase("e" + vars["name"], CGGeneric("Destroy%s();\n" % vars["name"]))
            )

            enumValues.append("e" + vars["name"])

            conversionToJS = self.getConversionToJS(vars, t)
            if conversionToJS:
                toJSValCases.append(
                    CGCase("e" + vars["name"], conversionToJS, CGCase.DONT_ADD_BREAK)
                )
            else:
                skipToJSVal = True

            assignmentCases.append(
                CGCase(
                    "e" + vars["name"],
                    CGGeneric(
                        "SetAs%s() = aOther.GetAs%s();\n" % (vars["name"], vars["name"])
                    ),
                )
            )
            moveCases.append(
                CGCase(
                    "e" + vars["name"],
                    CGGeneric(
                        "mType = e%s;\n" % vars["name"]
                        + "mValue.m%s.SetValue(std::move(aOther.mValue.m%s.Value()));\n"
                        % (vars["name"], vars["name"])
                    ),
                )
            )
            if self.ownsMembers and typeNeedsRooting(t):
                if t.isObject():
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                'JS::TraceRoot(trc, %s, "%s");\n'
                                % (
                                    "&mValue.m" + vars["name"] + ".Value()",
                                    "mValue.m" + vars["name"],
                                )
                            ),
                        )
                    )
                elif t.isDictionary():
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                "mValue.m%s.Value().TraceDictionary(trc);\n"
                                % vars["name"]
                            ),
                        )
                    )
                elif t.isSequence():
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                "DoTraceSequence(trc, mValue.m%s.Value());\n"
                                % vars["name"]
                            ),
                        )
                    )
                elif t.isRecord():
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                "TraceRecord(trc, mValue.m%s.Value());\n" % vars["name"]
                            ),
                        )
                    )
                else:
                    assert t.isSpiderMonkeyInterface()
                    traceCases.append(
                        CGCase(
                            "e" + vars["name"],
                            CGGeneric(
                                "mValue.m%s.Value().TraceSelf(trc);\n" % vars["name"]
                            ),
                        )
                    )

        dtor = CGSwitch("mType", destructorCases).define()

        methods.extend(getUnionInitMethods(self.type, isOwningUnion=self.ownsMembers))
        methods.append(
            ClassMethod(
                "Uninit",
                "void",
                [],
                visibility="public",
                body=dtor,
                bodyInHeader=not self.ownsMembers,
                inline=not self.ownsMembers,
            )
        )

        if not skipToJSVal:
            methods.append(
                ClassMethod(
                    "ToJSVal",
                    "bool",
                    [
                        Argument("JSContext*", "cx"),
                        Argument("JS::Handle<JSObject*>", "scopeObj"),
                        Argument("JS::MutableHandle<JS::Value>", "rval"),
                    ],
                    body=CGSwitch(
                        "mType", toJSValCases, default=CGGeneric("return false;\n")
                    ).define(),
                    const=True,
                )
            )

        constructors = [ctor]
        selfName = CGUnionStruct.unionTypeName(self.type, self.ownsMembers)
        if self.ownsMembers:
            if traceCases:
                traceBody = CGSwitch(
                    "mType", traceCases, default=CGGeneric("")
                ).define()
                methods.append(
                    ClassMethod(
                        "TraceUnion",
                        "void",
                        [Argument("JSTracer*", "trc")],
                        body=traceBody,
                    )
                )

            op_body = CGList([])
            op_body.append(CGSwitch("aOther.mType", moveCases))
            constructors.append(
                ClassConstructor(
                    [Argument("%s&&" % selfName, "aOther")],
                    visibility="public",
                    body=op_body.define(),
                )
            )

            methods.append(
                ClassMethod(
                    "operator=",
                    "%s&" % selfName,
                    [Argument("%s&&" % selfName, "aOther")],
                    body="this->~%s();\nnew (this) %s (std::move(aOther));\nreturn *this;\n"
                    % (selfName, selfName),
                )
            )

            body = dedent(
                """
                MOZ_RELEASE_ASSERT(mType != eUninitialized);
                return static_cast<Type>(mType);
                """
            )
            methods.append(
                ClassMethod(
                    "GetType",
                    "Type",
                    [],
                    bodyInHeader=True,
                    body=body,
                    const=True,
                )
            )

            if CGUnionStruct.isUnionCopyConstructible(self.type):
                constructors.append(
                    ClassConstructor(
                        [Argument("const %s&" % selfName, "aOther")],
                        bodyInHeader=True,
                        visibility="public",
                        explicit=True,
                        body="*this = aOther;\n",
                    )
                )
                op_body = CGList([])
                op_body.append(CGSwitch("aOther.mType", assignmentCases))
                op_body.append(CGGeneric("return *this;\n"))
                methods.append(
                    ClassMethod(
                        "operator=",
                        "%s&" % selfName,
                        [Argument("const %s&" % selfName, "aOther")],
                        body=op_body.define(),
                    )
                )
                disallowCopyConstruction = False
            else:
                disallowCopyConstruction = True
        else:
            disallowCopyConstruction = True

        if self.ownsMembers and idlTypeNeedsCycleCollection(self.type):
            friend = (
                "  friend void ImplCycleCollectionUnlink(%s& aUnion);\n"
                % CGUnionStruct.unionTypeName(self.type, True)
            )
        else:
            friend = ""

        enumValuesNoUninit = [x for x in enumValues if x != "eUninitialized"]

        enums = [
            ClassGroup(
                [
                    ClassEnum("TypeOrUninit", enumValues, visibility="private"),
                    ClassEnum(
                        "Type",
                        enumValuesNoUninit,
                        visibility="public",
                        enumClass=True,
                        values=["TypeOrUninit::" + x for x in enumValuesNoUninit],
                    ),
                ]
            )
        ]

        bases = [
            ClassBase("AllOwningUnionBase" if self.ownsMembers else "AllUnionBase")
        ]

        typeAliases = []
        bufferSourceTypes = [
            t.name for t in self.type.flatMemberTypes if t.isBufferSource()
        ]
        if len(bufferSourceTypes) > 0:
            bases.append(ClassBase("UnionWithTypedArraysBase"))
            memberTypesCount = len(self.type.flatMemberTypes)
            if self.type.hasNullableType:
                memberTypesCount += 1

            typeAliases = [
                ClassUsingDeclaration(
                    "ApplyToTypedArrays",
                    "binding_detail::ApplyToTypedArraysHelper<%s, %s, %s>"
                    % (
                        selfName,
                        toStringBool(memberTypesCount > len(bufferSourceTypes)),
                        ", ".join(bufferSourceTypes),
                    ),
                )
            ]

        return CGClass(
            selfName,
            bases=bases,
            typeAliases=typeAliases,
            members=members,
            constructors=constructors,
            methods=methods,
            disallowCopyConstruction=disallowCopyConstruction,
            extradeclarations=friend,
            destructor=ClassDestructor(
                visibility="public", body="Uninit();\n", bodyInHeader=True
            ),
            enums=enums,
            unions=[ClassUnion("Value", unionValues, visibility="private")],
        )

    def getConversionToJS(self, templateVars, type):
        if type.isDictionary() and not type.inner.needsConversionToJS:
            # We won't be able to convert this dictionary to a JS value, nor
            # will we need to, since we don't need a ToJSVal method at all.
            return None

        assert not type.nullable()  # flatMemberTypes never has nullable types
        val = "mValue.m%(name)s.Value()" % templateVars
        wrapCode = wrapForType(
            type,
            self.descriptorProvider,
            {
                "jsvalRef": "rval",
                "jsvalHandle": "rval",
                "obj": "scopeObj",
                "result": val,
                "spiderMonkeyInterfacesAreStructs": True,
            },
        )
        return CGGeneric(wrapCode)

    @staticmethod
    def isUnionCopyConstructible(type):
        return all(isTypeCopyConstructible(t) for t in type.flatMemberTypes)

    @staticmethod
    def unionTypeName(type, ownsMembers):
        """
        Returns a string name for this known union type.
        """
        assert type.isUnion() and not type.nullable()
        return ("Owning" if ownsMembers else "") + type.name

    @staticmethod
    def unionTypeDecl(type, ownsMembers):
        """
        Returns a string for declaring this possibly-nullable union type.
        """
        assert type.isUnion()
        nullable = type.nullable()
        if nullable:
            type = type.inner
        decl = CGGeneric(CGUnionStruct.unionTypeName(type, ownsMembers))
        if nullable:
            decl = CGTemplatedType("Nullable", decl)
        return decl.define()


class ClassItem:
    """Use with CGClass"""

    def __init__(self, name, visibility):
        self.name = name
        self.visibility = visibility

    def declare(self, cgClass):
        assert False

    def define(self, cgClass):
        assert False


class ClassBase(ClassItem):
    def __init__(self, name, visibility="public"):
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        return "%s %s" % (self.visibility, self.name)

    def define(self, cgClass):
        # Only in the header
        return ""


class ClassMethod(ClassItem):
    def __init__(
        self,
        name,
        returnType,
        args,
        inline=False,
        static=False,
        virtual=False,
        const=False,
        bodyInHeader=False,
        templateArgs=None,
        visibility="public",
        body=None,
        breakAfterReturnDecl="\n",
        breakAfterSelf="\n",
        override=False,
        canRunScript=False,
        noDiscard=False,
        delete=False,
    ):
        """
        override indicates whether to flag the method as override
        """
        assert not override or virtual
        assert not (override and static)
        assert not (delete and body)
        self.returnType = returnType
        self.args = args
        self.inline = inline or bodyInHeader
        self.static = static
        self.virtual = virtual
        self.const = const
        self.bodyInHeader = bodyInHeader
        self.templateArgs = templateArgs
        self.body = body
        self.breakAfterReturnDecl = breakAfterReturnDecl
        self.breakAfterSelf = breakAfterSelf
        self.override = override
        self.canRunScript = canRunScript
        self.noDiscard = noDiscard
        self.delete = delete
        ClassItem.__init__(self, name, visibility)

    def getDecorators(self, declaring):
        decorators = []
        if self.noDiscard:
            decorators.append("[[nodiscard]]")
        if self.canRunScript:
            decorators.append("MOZ_CAN_RUN_SCRIPT")
        if self.inline:
            decorators.append("inline")
        if declaring:
            if self.static:
                decorators.append("static")
            if self.virtual and not self.override:
                decorators.append("virtual")
        if decorators:
            return " ".join(decorators) + " "
        return ""

    def getBody(self):
        # Override me or pass a string to constructor
        assert self.body is not None
        return self.body

    def declare(self, cgClass):
        templateClause = (
            "template <%s>\n" % ", ".join(self.templateArgs)
            if self.bodyInHeader and self.templateArgs
            else ""
        )
        args = ", ".join([a.declare() for a in self.args])
        if self.delete:
            body = " = delete;\n"
        elif self.bodyInHeader:
            body = indent(self.getBody())
            body = "\n{\n" + body + "}\n"
        else:
            body = ";\n"

        return fill(
            "${templateClause}${decorators}${returnType}${breakAfterReturnDecl}"
            "${name}(${args})${const}${override}${body}"
            "${breakAfterSelf}",
            templateClause=templateClause,
            decorators=self.getDecorators(True),
            returnType=self.returnType,
            breakAfterReturnDecl=self.breakAfterReturnDecl,
            name=self.name,
            args=args,
            const=" const" if self.const else "",
            override=" override" if self.override else "",
            body=body,
            breakAfterSelf=self.breakAfterSelf,
        )

    def define(self, cgClass):
        if self.delete or self.bodyInHeader:
            return ""

        templateArgs = cgClass.templateArgs
        if templateArgs:
            if cgClass.templateSpecialization:
                templateArgs = templateArgs[len(cgClass.templateSpecialization) :]

        if templateArgs:
            templateClause = "template <%s>\n" % ", ".join(
                [str(a) for a in templateArgs]
            )
        else:
            templateClause = ""

        return fill(
            """
            ${templateClause}${decorators}${returnType}
            ${className}::${name}(${args})${const}
            {
              $*{body}
            }
            """,
            templateClause=templateClause,
            decorators=self.getDecorators(False),
            returnType=self.returnType,
            className=cgClass.getNameString(),
            name=self.name,
            args=", ".join([a.define() for a in self.args]),
            const=" const" if self.const else "",
            body=self.getBody(),
        )


class ClassUsingDeclaration(ClassItem):
    """
    Used for declaring an alias for a type in a CGClass

    name is the name of the alias

    type is the type to declare an alias of

    visibility determines the visibility of the alias (public,
    protected, private), defaults to public.
    """

    def __init__(self, name, type, visibility="public"):
        self.type = type
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        return "using %s = %s;\n\n" % (self.name, self.type)

    def define(self, cgClass):
        return ""


class ClassUsingFromBaseDeclaration(ClassItem):
    """
    Used for importing a name from a base class into a CGClass

    baseClass is the name of the base class to import the name from

    name is the name to import

    visibility determines the visibility of the name (public,
    protected, private), defaults to public.
    """

    def __init__(self, baseClass, name, visibility="public"):
        self.baseClass = baseClass
        ClassItem.__init__(self, name, visibility)

    def declare(self, cgClass):
        return "using %s::%s;\n\n" % (self.baseClass, self.name)

    def define(self, cgClass):
        return ""


class ClassConstructor(ClassItem):
    """
    Used for adding a constructor to a CGClass.

    args is a list of Argument objects that are the arguments taken by the
    constructor.

    inline should be True if the constructor should be marked inline.

    bodyInHeader should be True if the body should be placed in the class
    declaration in the header.

    default should be True if the definition of the constructor should be
    `= default;`.

    visibility determines the visibility of the constructor (public,
    protected, private), defaults to private.

    explicit should be True if the constructor should be marked explicit.

    baseConstructors is a list of strings containing calls to base constructors,
    defaults to None.

    body contains a string with the code for the constructor, defaults to empty.
    """

    def __init__(
        self,
        args,
        inline=False,
        bodyInHeader=False,
        default=False,
        visibility="private",
        explicit=False,
        constexpr=False,
        baseConstructors=None,
        body="",
    ):
        assert not (inline and constexpr)
        assert not (bodyInHeader and constexpr)
        assert not (default and body)
        self.args = args
        self.inline = inline or bodyInHeader
        self.bodyInHeader = bodyInHeader or constexpr or default
        self.default = default
        self.explicit = explicit
        self.constexpr = constexpr
        self.baseConstructors = baseConstructors or []
        self.body = body
        ClassItem.__init__(self, None, visibility)

    def getDecorators(self, declaring):
        decorators = []
        if declaring:
            if self.explicit:
                decorators.append("explicit")
            if self.inline:
                decorators.append("inline")
            if self.constexpr:
                decorators.append("constexpr")
        if decorators:
            return " ".join(decorators) + " "
        return ""

    def getInitializationList(self, cgClass):
--> --------------------

--> maximum size reached

--> --------------------