dom/bindings/Codegen.py
author Boris Zbarsky <bzbarsky@mit.edu>
Sat, 04 May 2013 21:44:10 -0400
changeset 130861 1a60a6e9d9b8bd5f6efb50f35410974236a58e7b
parent 130860 1531a6ec12c179ea3b8614f10f4f231081081517
child 130899 334e63a273cbbe23ed26a144a4c6d9a48e65a5b9
permissions -rw-r--r--
Bug 865785 part 2. Fix rooting issues in JS-implemented webidl. r=mccr8

# 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 operator
import os
import re
import string
import math

from WebIDL import BuiltinTypes, IDLBuiltinType, IDLNullValue, IDLSequenceType, IDLType
from Configuration import NoSuchDescriptorError, getTypesFromDescriptor, getTypesFromDictionary, getTypesFromCallback, Descriptor

AUTOGENERATED_WARNING_COMMENT = \
    "/* THIS FILE IS AUTOGENERATED - DO NOT EDIT */\n\n"
ADDPROPERTY_HOOK_NAME = '_addProperty'
FINALIZE_HOOK_NAME = '_finalize'
TRACE_HOOK_NAME = '_trace'
CONSTRUCT_HOOK_NAME = '_constructor'
LEGACYCALLER_HOOK_NAME = '_legacycaller'
HASINSTANCE_HOOK_NAME = '_hasInstance'
NEWRESOLVE_HOOK_NAME = '_newResolve'

def replaceFileIfChanged(filename, newContents):
    """
    Read a copy of the old file, so that we don't touch it if it hasn't changed.
    Returns True if the file was updated, false otherwise.
    """
    oldFileContents = ""
    try:
        oldFile = open(filename, 'rb')
        oldFileContents = ''.join(oldFile.readlines())
        oldFile.close()
    except:
        pass

    if newContents == oldFileContents:
        return False

    f = open(filename, 'wb')
    f.write(newContents)
    f.close()
    return True

def toStringBool(arg):
    return str(not not arg).lower()

def toBindingNamespace(arg):
    return re.sub("((_workers)?$)", "Binding\\1", arg);

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 CGNativePropertyHooks(CGThing):
    """
    Generate a NativePropertyHooks for a given descriptor
    """
    def __init__(self, descriptor, properties):
        CGThing.__init__(self)
        self.descriptor = descriptor
        self.properties = properties
    def declare(self):
        if self.descriptor.workers:
            return ""
        return "extern const NativePropertyHooks sNativePropertyHooks;\n"
    def define(self):
        if self.descriptor.workers:
            return ""
        if self.descriptor.concrete and self.descriptor.proxy:
            resolveOwnProperty = "ResolveOwnProperty"
            enumerateOwnProperties = "EnumerateOwnProperties"
        else:
            resolveOwnProperty = "nullptr"
            enumerateOwnProperties = "nullptr"
        if self.properties.hasNonChromeOnly():
            regular = "&sNativeProperties"
        else:
            regular = "nullptr"
        if self.properties.hasChromeOnly():
            chrome = "&sChromeOnlyNativeProperties"
        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"
        parent = self.descriptor.interface.parent
        parentHooks = ("&" + toBindingNamespace(parent.identifier.name) + "::sNativePropertyHooks"
                       if parent else 'NULL')

        return CGWrapper(CGIndenter(CGList([CGGeneric(resolveOwnProperty),
                                            CGGeneric(enumerateOwnProperties),
                                            CGWrapper(CGList([CGGeneric(regular),
                                                              CGGeneric(chrome)],
                                                             ", "),
                                                      pre="{ ", post=" }"),
                                            CGGeneric(prototypeID),
                                            CGGeneric(constructorID),
                                            CGGeneric(parentHooks)],
                                           ",\n")),
                         pre="const NativePropertyHooks sNativePropertyHooks = {\n",
                         post="\n};\n").define()

def NativePropertyHooks(descriptor):
    return "&sWorkerNativePropertyHooks" if descriptor.workers else "&sNativePropertyHooks"

def DOMClass(descriptor):
        protoList = ['prototypes::id::' + proto for proto in descriptor.prototypeChain]
        # 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)))
        prototypeChainString = ', '.join(protoList)
        if descriptor.workers or descriptor.nativeOwnership != 'refcounted':
            participant = "nullptr"
        else:
            participant = "NS_CYCLE_COLLECTION_PARTICIPANT(%s)" % descriptor.nativeType
        getParentObject = "GetParentObject<%s>::Get" % descriptor.nativeType
        return """{
  { %s },
  %s,
  %s,
  %s,
  GetProtoObject,
  %s
}""" % (prototypeChainString, toStringBool(descriptor.nativeOwnership == 'nsisupports'),
        NativePropertyHooks(descriptor),
        getParentObject,
        participant)

class CGDOMJSClass(CGThing):
    """
    Generate a DOMJSClass for a given descriptor
    """
    def __init__(self, descriptor):
        CGThing.__init__(self)
        self.descriptor = descriptor
        # Our current reserved slot situation is unsafe for globals. Fix bug 760095!
        assert "Window" not in descriptor.interface.identifier.name
    def declare(self):
        return "extern DOMJSClass Class;\n"
    def define(self):
        traceHook = TRACE_HOOK_NAME if self.descriptor.customTrace else 'nullptr'
        callHook = LEGACYCALLER_HOOK_NAME if self.descriptor.operations["LegacyCaller"] else 'nullptr'
        classFlags = "JSCLASS_IS_DOMJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(3)"
        if self.descriptor.interface.getExtendedAttribute("NeedNewResolve"):
            newResolveHook = "(JSResolveOp)" + NEWRESOLVE_HOOK_NAME
            classFlags += " | JSCLASS_NEW_RESOLVE"
        else:
            newResolveHook = "JS_ResolveStub"
        return """
DOMJSClass Class = {
  { "%s",
    %s,
    %s, /* addProperty */
    JS_DeletePropertyStub, /* delProperty */
    JS_PropertyStub,       /* getProperty */
    JS_StrictPropertyStub, /* setProperty */
    JS_EnumerateStub,
    %s,
    JS_ConvertStub,
    %s, /* finalize */
    NULL,                  /* checkAccess */
    %s, /* call */
    NULL,                  /* hasInstance */
    NULL,                  /* construct */
    %s, /* trace */
    JSCLASS_NO_INTERNAL_MEMBERS
  },
%s
};
""" % (self.descriptor.interface.identifier.name,
       classFlags,
       ADDPROPERTY_HOOK_NAME if self.descriptor.concrete and not self.descriptor.workers and self.descriptor.wrapperCache else 'JS_PropertyStub',
       newResolveHook, FINALIZE_HOOK_NAME, callHook, traceHook,
       CGIndenter(CGGeneric(DOMClass(self.descriptor))).define())

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

def UseHolderForUnforgeable(descriptor):
    return (descriptor.concrete and
            descriptor.proxy and
            any(m for m in descriptor.interface.members if m.isAttr() and m.isUnforgeable()))

def CallOnUnforgeableHolder(descriptor, code, isXrayCheck=None):
    """
    Generate the code to execute the code in "code" on an unforgeable holder if
    needed. code should be a string containing the code to execute. If it
    contains a ${holder} string parameter it will be replaced with the
    unforgeable holder object.

    If isXrayCheck is not None it should be a string that contains a statement
    returning whether proxy is an Xray. If isXrayCheck is None the generated
    code won't try to unwrap Xrays.
    """
    code = string.Template(code).substitute({ "holder": "unforgeableHolder" })
    if not isXrayCheck is None:
        pre = """// Scope for 'global', 'ac' and 'unforgeableHolder'
{
  JS::Rooted<JSObject*> global(cx);
  Maybe<JSAutoCompartment> ac;
  if (""" + isXrayCheck + """) {
    global = js::GetGlobalForObjectCrossCompartment(js::UncheckedUnwrap(proxy));
    ac.construct(cx, global);
  } else {
    global = js::GetGlobalForObjectCrossCompartment(proxy);
  }"""
    else:
        pre = """// Scope for 'global' and 'unforgeableHolder'
{
  JSObject* global = js::GetGlobalForObjectCrossCompartment(proxy);"""

    return (pre + """
  JS::Rooted<JSObject*> unforgeableHolder(cx, GetUnforgeableHolder(global, prototypes::id::%s));
""" + CGIndenter(CGGeneric(code)).define() + """
}
""") % descriptor.name

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"
        if UseHolderForUnforgeable(self.descriptor):
            slotCount += " + 1 /* slot for the JSObject holding the unforgeable properties */"
        return """static DOMIfaceAndProtoJSClass PrototypeClass = {
  {
    "%sPrototype",
    JSCLASS_IS_DOMIFACEANDPROTOJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(%s),
    JS_PropertyStub,       /* addProperty */
    JS_DeletePropertyStub, /* delProperty */
    JS_PropertyStub,       /* getProperty */
    JS_StrictPropertyStub, /* setProperty */
    JS_EnumerateStub,
    JS_ResolveStub,
    JS_ConvertStub,
    nullptr,               /* finalize */
    nullptr,               /* checkAccess */
    nullptr,               /* call */
    nullptr,               /* hasInstance */
    nullptr,               /* construct */
    nullptr,               /* trace */
    JSCLASS_NO_INTERNAL_MEMBERS
  },
  eInterfacePrototype,
  %s,
  "[object %sPrototype]",
  %s,
  %s
};
""" % (self.descriptor.interface.identifier.name, slotCount,
       NativePropertyHooks(self.descriptor),
       self.descriptor.interface.identifier.name,
       prototypeID, depth)

def NeedsGeneratedHasInstance(descriptor):
    return descriptor.hasXPConnectImpls or descriptor.interface.isConsequential()

class CGInterfaceObjectJSClass(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):
        if self.descriptor.interface.ctor():
            ctorname = CONSTRUCT_HOOK_NAME
        else:
            ctorname = "ThrowingConstructor"
        if NeedsGeneratedHasInstance(self.descriptor):
            hasinstance = HASINSTANCE_HOOK_NAME
        elif self.descriptor.interface.hasInterfacePrototypeObject():
            hasinstance = "InterfaceHasInstance"
        else:
            hasinstance = "nullptr"
        (prototypeID, depth) = PrototypeIDAndDepth(self.descriptor)
        slotCount = "DOM_INTERFACE_SLOTS_BASE"
        if len(self.descriptor.interface.namedConstructors) > 0:
            slotCount += (" + %i /* slots for the named constructors */" %
                          len(self.descriptor.interface.namedConstructors))
        return """
static DOMIfaceAndProtoJSClass InterfaceObjectClass = {
  {
    "Function",
    JSCLASS_IS_DOMIFACEANDPROTOJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(%s),
    JS_PropertyStub,       /* addProperty */
    JS_DeletePropertyStub, /* delProperty */
    JS_PropertyStub,       /* getProperty */
    JS_StrictPropertyStub, /* setProperty */
    JS_EnumerateStub,
    JS_ResolveStub,
    JS_ConvertStub,
    nullptr,               /* finalize */
    nullptr,               /* checkAccess */
    %s, /* call */
    %s, /* hasInstance */
    %s, /* construct */
    nullptr,               /* trace */
    JSCLASS_NO_INTERNAL_MEMBERS
  },
  eInterface,
  %s,
  "function %s() {\\n    [native code]\\n}",
  %s,
  %s
};
""" % (slotCount, ctorname,
       hasinstance, ctorname, NativePropertyHooks(self.descriptor),
       self.descriptor.interface.identifier.name,
       prototypeID, depth)

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)
        self.children = children
        self.joiner = joiner
    def append(self, child):
        self.children.append(child)
    def prepend(self, child):
        self.children.insert(0, child)
    def join(self, generator):
        return self.joiner.join(filter(lambda s: len(s) > 0, (child for child in generator)))
    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

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()

# We'll want to insert the indent at the beginnings of lines, but we
# don't want to indent empty lines.  So only indent lines that have a
# non-newline character on them.
lineStartDetector = re.compile("^(?=[^\n#])", re.MULTILINE)
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):
        CGThing.__init__(self)
        self.child = child
        self.indent = " " * indentLevel
        self.declareOnly = declareOnly
    def declare(self):
        decl = self.child.declare()
        if decl is not "":
            return re.sub(lineStartDetector, self.indent, decl)
        else:
            return ""
    def define(self):
        defn = self.child.define()
        if defn is not "" and not self.declareOnly:
            return re.sub(lineStartDetector, self.indent, defn)
        else:
            return defn

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:
            # We don't use lineStartDetector because we don't want to
            # insert whitespace at the beginning of our _first_ line.
            decl = stripTrailingWhitespace(
                decl.replace("\n", "\n" + (" " * len(self.declarePre))))
        return self.declarePre + decl + self.declarePost
    def define(self):
        if self.declareOnly:
            return ''
        defn = self.child.define()
        if self.reindent:
            # We don't use lineStartDetector because we don't want to
            # insert whitespace at the beginning of our _first_ line.
            defn = stripTrailingWhitespace(
                defn.replace("\n", "\n" + (" " * len(self.definePre))))
        return self.definePre + defn + self.definePost

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

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

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

class CGTemplatedType(CGWrapper):
    def __init__(self, templateName, child, isConst=False, isReference=False):
        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(CGWrapper):
    def __init__(self, namespace, child, declareOnly=False):
        pre = "namespace %s {\n" % namespace
        post = "} // namespace %s\n" % namespace
        CGWrapper.__init__(self, child, pre=pre, post=post,
                           declareOnly=declareOnly)
    @staticmethod
    def build(namespaces, child, declareOnly=False):
        """
        Static helper method to build multiple wrapped namespaces.
        """
        if not namespaces:
            return CGWrapper(child, declareOnly=declareOnly)
        inner = CGNamespace.build(namespaces[1:], child, declareOnly=declareOnly)
        return CGNamespace(namespaces[0], inner, declareOnly=declareOnly)

class CGIncludeGuard(CGWrapper):
    """
    Generates include guards for a header.
    """
    def __init__(self, prefix, child):
        """|prefix| is the filename without the extension."""
        define = 'mozilla_dom_%s_h__' % prefix
        CGWrapper.__init__(self, child,
                           declarePre='#ifndef %s\n#define %s\n\n' % (define, define),
                           declarePost='\n#endif // %s\n' % define)

def getRelevantProviders(descriptor, dictionary, config):
    assert not descriptor or not dictionary
    if descriptor is not None:
        return [descriptor]
    if dictionary is not None:
        # Do both the non-worker and worker versions
        return [
            config.getDescriptorProvider(False),
            config.getDescriptorProvider(True)
            ]
    # Do non-workers only for callbacks
    return [ config.getDescriptorProvider(False) ]

def callForEachType(descriptors, dictionaries, callbacks, func):
    for d in descriptors:
        if d.interface.isExternal():
            continue
        for t in getTypesFromDescriptor(d):
            func(t, descriptor=d)
    for dictionary in dictionaries:
        for t in getTypesFromDictionary(dictionary):
            func(t, dictionary=dictionary)
    for callback in callbacks:
        for t in getTypesFromCallback(callback):
            func(t)

class CGHeaders(CGWrapper):
    """
    Generates the appropriate include statements.
    """
    def __init__(self, descriptors, dictionaries, callbacks,
                 callbackDescriptors,
                 declareIncludes, defineIncludes, 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.
        """

        # Determine the filenames for which we need headers.
        interfaceDeps = [d.interface for d in descriptors]
        ancestors = []
        for iface in interfaceDeps:
            while iface.parent:
                ancestors.append(iface.parent)
                iface = iface.parent
        interfaceDeps.extend(ancestors)
        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())

        # Grab the includes for checking hasInstance
        interfacesImplementingSelf = set()
        for d in descriptors:
            interfacesImplementingSelf |= d.interface.interfacesImplementingSelf
        implementationIncludes |= set(self.getDeclarationFilename(i) for i in
                                      interfacesImplementingSelf)

         # Grab the includes for the things that involve XPCOM interfaces
        hasInstanceIncludes = set("nsIDOM" + d.interface.identifier.name + ".h" for d
                                  in descriptors if
                                  NeedsGeneratedHasInstance(d) and
                                  d.interface.hasInterfacePrototypeObject())

        # 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(t, descriptor=None, dictionary=None):
            """
            Add the relevant headers for this type.  We use descriptor and
            dictionary, if passed, to decide what to do with interface types.
            """
            assert not descriptor or not dictionary
            unrolled = t.unroll()
            if unrolled.isUnion():
                # UnionConversions.h includes UnionTypes.h
                bindingHeaders.add("mozilla/dom/UnionConversions.h")
            elif unrolled.isInterface():
                if unrolled.isSpiderMonkeyInterface():
                    bindingHeaders.add("jsfriendapi.h")
                    bindingHeaders.add("mozilla/dom/TypedArray.h")
                else:
                    providers = getRelevantProviders(descriptor, dictionary,
                                                     config)
                    for p in providers:
                        try:
                            typeDesc = p.getDescriptor(unrolled.inner.identifier.name)
                        except NoSuchDescriptorError:
                            continue
                        if dictionary:
                            # 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 nsRefPtr and have inline
                            # constructors/destructors.
                            #
                            # XXXbz maybe dictionaries with interface members
                            # should just have out-of-line constructors and
                            # destructors?
                            declareIncludes.add(typeDesc.headerFile)
                        else:
                            implementationIncludes.add(typeDesc.headerFile)
                        bindingHeaders.add(self.getDeclarationFilename(typeDesc.interface))
            elif unrolled.isDictionary():
                bindingHeaders.add(self.getDeclarationFilename(unrolled.inner))
            elif unrolled.isCallback():
                # Callbacks are both a type and an object
                bindingHeaders.add(self.getDeclarationFilename(t.unroll()))
            elif unrolled.isFloat() and not unrolled.isUnrestricted():
                # Restricted floats are tested for finiteness
                bindingHeaders.add("mozilla/FloatingPoint.h")

        callForEachType(descriptors + callbackDescriptors, dictionaries,
                        callbacks, addHeadersForType)

        # Now for non-callback descriptors make sure we include any
        # headers needed by Func declarations.
        for desc in descriptors:
            if desc.interface.isExternal():
                continue
            for m in desc.interface.members:
                func = PropertyDefiner.getStringAttr(m, "Func")
                # Include the right class header, which we can only do
                # if this is a class member function.
                if func is not None and "::" in func:
                    # Strip out the function name and convert "::" to "/"
                    bindingHeaders.add("/".join(func.split("::")[:-1]) + ".h")

        for d in dictionaries:
            if d.parent:
                declareIncludes.add(self.getDeclarationFilename(d.parent))
            bindingHeaders.add(self.getDeclarationFilename(d))

        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 BindingUtils.h so we can wrap "this" objects
            declareIncludes.add("mozilla/dom/BindingUtils.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 BindingUtils.h so we can wrap "this" objects
            declareIncludes.add("mozilla/dom/BindingUtils.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)

        if len(jsImplementedDescriptors) != 0:
            bindingHeaders.add("nsIDOMGlobalPropertyInitializer.h")

        # Let the machinery do its thing.
        def _includeString(includes):
            return ''.join(['#include "%s"\n' % i for i in includes]) + '\n'
        CGWrapper.__init__(self, child,
                           declarePre=_includeString(sorted(declareIncludes)),
                           definePre=_includeString(sorted(set(defineIncludes) |
                                                           bindingIncludes |
                                                           bindingHeaders |
                                                           hasInstanceIncludes |
                                                           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')

def SortedTuples(l):
    """
    Sort a list of tuples based on the first item in the tuple
    """
    return sorted(l, key=operator.itemgetter(0))

def SortedDictValues(d):
    """
    Returns a list of values from the dict sorted by key.
    """
    # Create a list of tuples containing key and value, sorted on key.
    d = SortedTuples(d.items())
    # We're only interested in the values.
    return (i[1] for i in d)

def UnionTypes(descriptors, dictionaries, callbacks, config):
    """
    Returns a tuple containing a set of header filenames to include in
    UnionTypes.h, a set of header filenames to include in UnionTypes.cpp, a set
    of tuples containing a type declaration and a boolean if the type is a
    struct for member types of the unions and a CGList containing CGUnionStructs
    for every union.
    """

    # Now find all the things we'll need as arguments and return values because
    # we need to wrap or unwrap them.
    headers = set()
    implheaders = set(["UnionTypes.h"])
    declarations = set()
    unionStructs = dict()

    def addInfoForType(t, descriptor=None, dictionary=None):
        """
        Add info for the given type.  descriptor and dictionary, if passed, are
        used to figure out what to do with interface types.
        """
        assert not descriptor or not dictionary
        t = t.unroll()
        if not t.isUnion():
            return
        name = str(t)
        if not name in unionStructs:
            providers = getRelevantProviders(descriptor, dictionary,
                                             config)
            # FIXME: Unions are broken in workers.  See bug 809899.
            unionStructs[name] = CGUnionStruct(t, providers[0])
            for f in t.flatMemberTypes:
                f = f.unroll()
                if f.isInterface():
                    if f.isSpiderMonkeyInterface():
                        headers.add("jsfriendapi.h")
                        headers.add("mozilla/dom/TypedArray.h")
                    else:
                        for p in providers:
                            try:
                                typeDesc = p.getDescriptor(f.inner.identifier.name)
                            except NoSuchDescriptorError:
                                continue
                            declarations.add((typeDesc.nativeType, False))
                            implheaders.add(typeDesc.headerFile)
                elif f.isDictionary():
                    declarations.add((f.inner.identifier.name, True))
                    implheaders.add(CGHeaders.getDeclarationFilename(f.inner))

    callForEachType(descriptors, dictionaries, callbacks, addInfoForType)

    return (headers, implheaders, declarations,
            CGList(SortedDictValues(unionStructs), "\n"))

def UnionConversions(descriptors, dictionaries, callbacks, config):
    """
    Returns a CGThing to declare all union argument conversion helper structs.
    """
    # Now find all the things we'll need as arguments because we
    # need to unwrap them.
    headers = set()
    unionConversions = dict()

    def addInfoForType(t, descriptor=None, dictionary=None):
        """
        Add info for the given type.  descriptor and dictionary, if passed, are
        used to figure out what to do with interface types.
        """
        assert not descriptor or not dictionary
        t = t.unroll()
        if not t.isUnion():
            return
        name = str(t)
        if not name in unionConversions:
            providers = getRelevantProviders(descriptor, dictionary,
                                             config)
            unionConversions[name] = CGUnionConversionStruct(t, providers[0])
            for f in t.flatMemberTypes:
                f = f.unroll()
                if f.isInterface():
                    if f.isSpiderMonkeyInterface():
                        headers.add("jsfriendapi.h")
                        headers.add("mozilla/dom/TypedArray.h")
                    elif not f.inner.isExternal():
                        headers.add(CGHeaders.getDeclarationFilename(f.inner))
                elif f.isDictionary():
                    headers.add(CGHeaders.getDeclarationFilename(f.inner))

    callForEachType(descriptors, dictionaries, callbacks, addInfoForType)

    return (headers,
            CGWrapper(CGList(SortedDictValues(unionConversions), "\n"),
                      post="\n\n"))

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.
    """
    def __init__(self, descriptor, name, returnType, args, inline=False, alwaysInline=False, static=False, templateArgs=None):
        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
    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.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 declare(self):
        if self.inline:
            return self._define(True)
        return "%s%s%s(%s);\n" % (self._template(), self._decorators(), self.name, self._argstring(True))
    def _define(self, fromDeclare=False):
        return self.definition_prologue(fromDeclare) + "\n" + self.definition_body() + self.definition_epilogue()
    def define(self):
        return "" if self.inline else self._define()
    def definition_prologue(self, fromDeclare):
        return "%s%s%s(%s)\n{" % (self._template(), self._decorators(),
                                  self.name, self._argstring(fromDeclare))
    def definition_epilogue(self):
        return "\n}\n"
    def definition_body(self):
        assert(False) # Override me!

class CGAbstractStaticMethod(CGAbstractMethod):
    """
    Abstract base class for codegen of implementation-only (no
    declaration) static methods.
    """
    def __init__(self, descriptor, name, returnType, args):
        CGAbstractMethod.__init__(self, descriptor, name, returnType, args,
                                  inline=False, static=True)
    def declare(self):
        # We only have implementation
        return ""

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):
        if self.descriptor.nativeOwnership == 'nsisupports':
            assertion = ('  MOZ_STATIC_ASSERT((IsBaseOf<nsISupports, %s>::value), '
                         '"Must be an nsISupports class");') % self.descriptor.nativeType
        else:
            assertion = ''
        return """%s
  %s* self = UnwrapDOMObject<%s>(obj);
""" % (assertion, self.descriptor.nativeType, self.descriptor.nativeType)

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

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

class CGAddPropertyHook(CGAbstractClassHook):
    """
    A hook for addProperty, used to preserve our wrapper from GC.
    """
    def __init__(self, descriptor):
        args = [Argument('JSContext*', 'cx'), Argument('JSHandleObject', 'obj'),
                Argument('JSHandleId', 'id'), Argument('JSMutableHandleValue', 'vp')]
        CGAbstractClassHook.__init__(self, descriptor, ADDPROPERTY_HOOK_NAME,
                                     'JSBool', args)

    def generate_code(self):
        assert not self.descriptor.workers and self.descriptor.wrapperCache
        if self.descriptor.nativeOwnership == 'nsisupports':
            preserveArgs = "reinterpret_cast<nsISupports*>(self), self"
        else:
            preserveArgs = "self, self, NS_CYCLE_COLLECTION_PARTICIPANT(%s)" % self.descriptor.nativeType
        return ("  // We don't want to preserve if we don't have a wrapper.\n"
                "  if (self->GetWrapperPreserveColor()) {\n"
                "    nsContentUtils::PreserveWrapper(%s);\n"
                "  }\n"
                "  return true;" % preserveArgs)

def DeferredFinalizeSmartPtr(descriptor):
    if descriptor.nativeOwnership == 'owned':
        smartPtr = 'nsAutoPtr<%s>'
    else:
        assert descriptor.nativeOwnership == 'refcounted'
        smartPtr = 'nsRefPtr<%s>'
    return smartPtr % descriptor.nativeType

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

    def declare(self):
        return ""

    def define(self):
        return """nsTArray<%s >* sDeferredFinalizePointers;
""" % DeferredFinalizeSmartPtr(self.descriptor)

class CGGetDeferredFinalizePointers(CGAbstractStaticMethod):
    def __init__(self, descriptor):
        CGAbstractStaticMethod.__init__(self, descriptor, "GetDeferredFinalizePointers", "void*", [])

    def definition_body(self):
        return """  nsTArray<%s >* pointers = sDeferredFinalizePointers;
  sDeferredFinalizePointers = nullptr;
  return pointers;""" % DeferredFinalizeSmartPtr(self.descriptor)

class CGDeferredFinalize(CGAbstractStaticMethod):
    def __init__(self, descriptor):
        CGAbstractStaticMethod.__init__(self, descriptor, "DeferredFinalize", "bool", [Argument('uint32_t', 'slice'), Argument('void*', 'data')])

    def definition_body(self):
        smartPtr = DeferredFinalizeSmartPtr(self.descriptor)
        return """  MOZ_ASSERT(slice > 0, "nonsensical/useless call with slice == 0");
  nsTArray<%(smartPtr)s >* pointers = static_cast<nsTArray<%(smartPtr)s >*>(data);
  uint32_t oldLen = pointers->Length();
  slice = std::min(oldLen, slice);
  uint32_t newLen = oldLen - slice;
  pointers->RemoveElementsAt(newLen, slice);
  if (newLen == 0) {
    delete pointers;
    return true;
  }
  return false;""" % { 'smartPtr': smartPtr }

def finalizeHook(descriptor, hookName, context):
    if descriptor.customFinalize:
        finalize = "self->%s(%s);" % (hookName, context)
    else:
        finalize = "JSBindingFinalized<%s>::Finalized(self);\n" % descriptor.nativeType
        if descriptor.wrapperCache:
            finalize += "ClearWrapper(self, self);\n"
        if descriptor.interface.getExtendedAttribute('OverrideBuiltins'):
            finalize += "self->mExpandoAndGeneration.expando = JS::UndefinedValue();\n"
        if descriptor.workers:
            finalize += "self->Release();"
        elif descriptor.nativeOwnership == 'nsisupports':
            finalize += """XPCJSRuntime *rt = nsXPConnect::GetRuntimeInstance();
if (rt) {
  rt->DeferredRelease(reinterpret_cast<nsISupports*>(self));
} else {
  NS_RELEASE(self);
}"""
        else:
            smartPtr = DeferredFinalizeSmartPtr(descriptor)
            finalize += """static bool registered = false;
if (!registered) {
  XPCJSRuntime *rt = nsXPConnect::GetRuntimeInstance();
  if (!rt) {
    %(smartPtr)s dying;
    Take(dying, self);
    return;
  }
  rt->RegisterDeferredFinalize(GetDeferredFinalizePointers, DeferredFinalize);
  registered = true;
}
if (!sDeferredFinalizePointers) {
  sDeferredFinalizePointers = new nsAutoTArray<%(smartPtr)s, 16>();
}
%(smartPtr)s* defer = sDeferredFinalizePointers->AppendElement();
if (!defer) {
  %(smartPtr)s dying;
  Take(dying, self);
  return;
}
Take(*defer, self);""" % { 'smartPtr': smartPtr }
    return CGIfWrapper(CGGeneric(finalize), "self")

class CGClassFinalizeHook(CGAbstractClassHook):
    """
    A hook for finalize, used to release our native object.
    """
    def __init__(self, descriptor):
        args = [Argument('JSFreeOp*', 'fop'), Argument('JSObject*', 'obj')]
        CGAbstractClassHook.__init__(self, descriptor, FINALIZE_HOOK_NAME,
                                     'void', args)

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

class CGClassTraceHook(CGAbstractClassHook):
    """
    A hook to trace through our native object; used for GC and CC
    """
    def __init__(self, descriptor):
        args = [Argument('JSTracer*', 'trc'), Argument('JSObject*', 'obj')]
        CGAbstractClassHook.__init__(self, descriptor, TRACE_HOOK_NAME, 'void',
                                     args)

    def generate_code(self):
        return """  if (self) {
    self->%s(%s);
  }""" % (self.name, self.args[0].name)

class CGClassConstructor(CGAbstractStaticMethod):
    """
    JS-visible constructor for our objects
    """
    def __init__(self, descriptor, ctor, name=CONSTRUCT_HOOK_NAME):
        args = [Argument('JSContext*', 'cx'), Argument('unsigned', 'argc'), Argument('JS::Value*', 'vp')]
        CGAbstractStaticMethod.__init__(self, descriptor, name, 'JSBool', args)
        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):
        preamble = """
  JS::Rooted<JSObject*> obj(cx, JSVAL_TO_OBJECT(JS_CALLEE(cx, vp)));
"""
        name = self._ctor.identifier.name
        nativeName = MakeNativeName(self.descriptor.binaryNames.get(name, name))
        callGenerator = CGMethodCall(nativeName, True, self.descriptor,
                                     self._ctor, isConstructor=True)
        return preamble + callGenerator.define();

# Encapsulate the constructor in a helper method to share genConstructorBody with CGJSImplMethod.
class CGConstructNavigatorObjectHelper(CGAbstractStaticMethod):
    """
    Construct a new JS-implemented WebIDL DOM object, for use on navigator.
    """
    def __init__(self, descriptor):
        name = "ConstructNavigatorObjectHelper"
        args = [Argument('JSContext*', 'cx'),
                Argument('GlobalObject&', 'global'),
                Argument('ErrorResult&', 'aRv')]
        rtype = 'already_AddRefed<%s>' % descriptor.name
        CGAbstractStaticMethod.__init__(self, descriptor, name, rtype, args)

    def definition_body(self):
        return genConstructorBody(self.descriptor)

class CGConstructNavigatorObject(CGAbstractMethod):
    """
    Wrap a JS-implemented WebIDL object into a JS value, for use on navigator.
    """
    def __init__(self, descriptor):
        name = 'ConstructNavigatorObject'
        args = [Argument('JSContext*', 'aCx'), Argument('JS::Handle<JSObject*>', 'aObj')]
        CGAbstractMethod.__init__(self, descriptor, name, 'JSObject*', args)

    def definition_body(self):
        if not self.descriptor.interface.isJSImplemented():
            raise TypeError("Only JS-implemented classes are currently supported "
                            "on navigator. See bug 856820.")
        return string.Template("""  GlobalObject global(aCx, aObj);
  if (global.Failed()) {
    return nullptr;
  }
  ErrorResult rv;
  nsRefPtr<mozilla::dom::${descriptorName}> result = ConstructNavigatorObjectHelper(aCx, global, rv);
  rv.WouldReportJSException();
  if (rv.Failed()) {
    ThrowMethodFailedWithDetails<${mainThread}>(aCx, rv, "${descriptorName}", "navigatorConstructor");
    return nullptr;
  }
  JS::Rooted<JS::Value> v(aCx);
  if (!WrapNewBindingObject(aCx, aObj, result, v.address())) {
    MOZ_ASSERT(JS_IsExceptionPending(aCx));
    return nullptr;
  }
  return &v.toObject();""").substitute(
    {
        'descriptorName' : self.descriptor.name,
        'mainThread' : toStringBool(not self.descriptor.workers),
    })

class CGClassConstructHookHolder(CGGeneric):
    def __init__(self, descriptor):
        if descriptor.interface.ctor():
            constructHook = CONSTRUCT_HOOK_NAME
        else:
            constructHook = "ThrowingConstructor"
        CGGeneric.__init__(self,
                           "static const JSNativeHolder " + CONSTRUCT_HOOK_NAME + "_holder = {\n" +
                           "  " + constructHook + ",\n" +
                           "  " + NativePropertyHooks(descriptor) + "\n" +
                           "};\n")

def NamedConstructorName(m):
    return '_' + m.identifier.name

class CGNamedConstructors(CGThing):
    def __init__(self, descriptor):
        self.descriptor = descriptor
        CGThing.__init__(self)
    def declare(self):
        return ""
    def define(self):
        if len(self.descriptor.interface.namedConstructors) == 0:
            return ""

        constructorID = "constructors::id::"
        if self.descriptor.interface.hasInterfaceObject():
            constructorID += self.descriptor.name
        else:
            constructorID += "_ID_Count"
        nativePropertyHooks = """const NativePropertyHooks sNamedConstructorNativePropertyHooks = {
    nullptr,
    nullptr,
    { nullptr, nullptr },
    prototypes::id::%s,
    %s,
    nullptr
};

""" % (self.descriptor.name, constructorID)
        namedConstructors = CGList([], ",\n")
        for n in self.descriptor.interface.namedConstructors:
            namedConstructors.append(CGGeneric("{ \"%s\", { %s, &sNamedConstructorNativePropertyHooks }, %i }" % (n.identifier.name, NamedConstructorName(n), methodLength(n))))
        namedConstructors.append(CGGeneric("{ nullptr, { nullptr, nullptr }, 0 }"))
        namedConstructors = CGWrapper(CGIndenter(namedConstructors),
                                      pre="static const NamedConstructor namedConstructors[] = {\n",
                                      post="\n};\n")
        return nativePropertyHooks + namedConstructors.define()

class CGClassHasInstanceHook(CGAbstractStaticMethod):
    def __init__(self, descriptor):
        args = [Argument('JSContext*', 'cx'), Argument('JSHandleObject', 'obj'),
                Argument('JSMutableHandleValue', 'vp'), Argument('JSBool*', 'bp')]
        CGAbstractStaticMethod.__init__(self, descriptor, HASINSTANCE_HOOK_NAME,
                                        'JSBool', args)

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

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

    def generate_code(self):
        assert self.descriptor.nativeOwnership == 'nsisupports'
        header = """
  if (!vp.isObject()) {
    *bp = false;
    return true;
  }

  JS::Rooted<JSObject*> instance(cx, &vp.toObject());
  """
        if self.descriptor.interface.hasInterfacePrototypeObject():
            return header + """
  bool ok = InterfaceHasInstance(cx, obj, instance, bp);
  if (!ok || *bp) {
    return ok;
  }

  // FIXME Limit this to chrome by checking xpc::AccessCheck::isChrome(obj).
  nsISupports* native =
    nsContentUtils::XPConnect()->GetNativeOfWrapper(cx,
                                                    js::UncheckedUnwrap(instance));
  nsCOMPtr<nsIDOM%s> qiResult = do_QueryInterface(native);
  *bp = !!qiResult;
  return true;
         """ % self.descriptor.interface.identifier.name

        hasInstanceCode = """
  const DOMClass* domClass = GetDOMClass(js::UncheckedUnwrap(instance));
  *bp = false;
  if (!domClass) {
    // Not a DOM object, so certainly not an instance of this interface
    return true;
  }
  """
        # Sort interaces implementing self by name so we get stable output.
        for iface in sorted(self.descriptor.interface.interfacesImplementingSelf,
                            key=lambda iface: iface.identifier.name):
            hasInstanceCode += """
  if (domClass->mInterfaceChain[PrototypeTraits<prototypes::id::%s>::Depth] == prototypes::id::%s) {
    *bp = true;
    return true;
  }
""" % (iface.identifier.name, iface.identifier.name)
        hasInstanceCode += "  return true;"
        return header + hasInstanceCode;

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

class MemberCondition:
    """
    An object representing the condition for a member to actually be
    exposed.  Either pref or func or both can be None.  If not None,
    they should be strings that have the pref name or function name.
    """
    def __init__(self, pref, func):
        assert pref is None or isinstance(pref, str)
        assert func is None or isinstance(func, str)
        self.pref = pref
        if func is None:
            self.func = "nullptr"
        else:
            self.func = "&" + func

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

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

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
        # self.prefCacheData will store an array of (prefname, bool*)
        # pairs for our bool var caches.  generateArray will fill it
        # in as needed.
        self.prefCacheData = []
    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):
        # No Xrays in workers.
        return not self.descriptor.workers

    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),
                                 self.usedForXrays())
        if self.hasChromeOnly():
            str += self.generateArray(self.chrome, self.variableName(True),
                                      self.usedForXrays())
        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) is 1)
        assert(attr[0] is not None)
        return attr[0]

    @staticmethod
    def getControllingCondition(interfaceMember):
        return MemberCondition(PropertyDefiner.getStringAttr(interfaceMember,
                                                             "Pref"),
                               PropertyDefiner.getStringAttr(interfaceMember,
                                                             "Func"))

    def generatePrefableArray(self, array, name, specTemplate, specTerminator,
                              specType, getCondition, getDataTuple, doIdArrays):
        """
        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

        specTemplate is a template for each entry of the spec array

        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 for substitution into specTemplate.
        """

        # 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) is not 0)
        lastCondition = getCondition(array[0]) # So we won't put a specTerminator
                                               # at the very front of the list.
        specs = []
        prefableSpecs = []

        prefableTemplate = '  { true, %s, &%s[%d] }'
        prefCacheTemplate = '&%s[%d].enabled'
        def switchToCondition(props, condition):
            # Remember the info about where our pref-controlled
            # booleans live.
            if condition.pref is not None:
                props.prefCacheData.append(
                    (condition.pref,
                     prefCacheTemplate % (name, len(prefableSpecs)))
                    )
            # Set up pointers to the new sets of specs inside prefableSpecs
            prefableSpecs.append(prefableTemplate %
                                 (condition.func, name + "_specs", len(specs)))

        switchToCondition(self, lastCondition)

        for member in array:
            curCondition = getCondition(member)
            if lastCondition != curCondition:
                # Terminate previous list
                specs.append(specTerminator)
                # And switch to our new pref
                switchToCondition(self, curCondition)
                lastCondition = curCondition
            # And the actual spec
            specs.append(specTemplate % getDataTuple(member))
        specs.append(specTerminator)
        prefableSpecs.append("  { false, NULL }");

        specType = "const " + specType
        arrays = (("static %s %s_specs[] = {\n" +
                   ',\n'.join(specs) + "\n" +
                   "};\n\n" +
                   "// Can't be const because the pref-enabled boolean needs to be writable\n"
                   "static Prefable<%s> %s[] = {\n" +
                   ',\n'.join(prefableSpecs) + "\n" +
                   "};\n\n") % (specType, name, specType, name))
        if doIdArrays:
            arrays += ("static jsid %s_ids[%i] = { JSID_VOID };\n\n" %
                       (name, len(specs)))
        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)

class MethodDefiner(PropertyDefiner):
    """
    A class for defining methods on a prototype object.
    """
    def __init__(self, descriptor, name, static):
        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
                       not m.isIdentifierLess()]
        else:
            methods = []
        self.chrome = []
        self.regular = []
        for m in methods:
            method = { "name": m.identifier.name,
                       "methodInfo": not m.isStatic(),
                       "length": methodLength(m),
                       "flags": "JSPROP_ENUMERATE",
                       "condition": PropertyDefiner.getControllingCondition(m) }
            if isChromeOnly(m):
                self.chrome.append(method)
            else:
                self.regular.append(method)

        # FIXME Check for an existing iterator on the interface first.
        if any(m.isGetter() and m.isIndexed() for m in methods):
            self.regular.append({"name": 'iterator',
                                 "methodInfo": False,
                                 "nativeName": "JS_ArrayIterator",
                                 "length": 0,
                                 "flags": "JSPROP_ENUMERATE",
                                 "condition": MemberCondition(None, None) })

        if (not descriptor.interface.parent and not static and
            descriptor.nativeOwnership == 'nsisupports' and
            descriptor.interface.hasInterfacePrototypeObject()):
            self.chrome.append({"name": 'QueryInterface',
                                "methodInfo": False,
                                "length": 1,
                                "flags": "0",
                                "condition": MemberCondition(None, None) })

        if not static:
            stringifier = descriptor.operations['Stringifier']
            if stringifier:
                toStringDesc = { "name": "toString",
                                 "nativeName": stringifier.identifier.name,
                                 "length": 0,
                                 "flags": "JSPROP_ENUMERATE",
                                 "condition": PropertyDefiner.getControllingCondition(stringifier) }
                if isChromeOnly(stringifier):
                    self.chrome.append(toStringDesc)
                else:
                    self.regular.append(toStringDesc)

        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()

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

        def condition(m):
            return m["condition"]

        def specData(m):
            accessor = m.get("nativeName", m["name"])
            if m.get("methodInfo", True):
                jitinfo = ("&%s_methodinfo" % accessor)
                accessor = "genericMethod"
            else:
                jitinfo = "nullptr"
            return (m["name"], accessor, jitinfo, m["length"], m["flags"])

        return self.generatePrefableArray(
            array, name,
            '  JS_FNINFO("%s", %s, %s, %s, %s)',
            '  JS_FS_END',
            'JSFunctionSpec',
            condition, specData, doIdArrays)

class AttrDefiner(PropertyDefiner):
    def __init__(self, descriptor, name, 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:
            attributes = [m for m in descriptor.interface.members if
                          m.isAttr() and m.isStatic() == static and
                          m.isUnforgeable() == unforgeable]
        else:
            attributes = []
        self.chrome = [m for m in attributes if isChromeOnly(m)]
        self.regular = [m for m in attributes if not isChromeOnly(m)]
        self.static = static
        self.unforgeable = unforgeable

        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()

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

        def flags(attr):
            unforgeable = " | JSPROP_PERMANENT" if self.unforgeable else ""
            return ("JSPROP_SHARED | JSPROP_ENUMERATE | JSPROP_NATIVE_ACCESSORS" +
                    unforgeable)

        def getter(attr):
            if self.static:
                accessor = 'get_' + attr.identifier.name
                jitinfo = "nullptr"
            else:
                accessor = ("genericLenientGetter" if attr.hasLenientThis()
                            else "genericGetter")
                jitinfo = "&%s_getterinfo" % attr.identifier.name
            return "{ (JSPropertyOp)%s, %s }" % (accessor, jitinfo)

        def setter(attr):
            if attr.readonly and attr.getExtendedAttribute("PutForwards") is None:
                return "JSOP_NULLWRAPPER"
            if self.static:
                accessor = 'set_' + attr.identifier.name
                jitinfo = "nullptr"
            else:
                accessor = ("genericLenientSetter" if attr.hasLenientThis()
                            else "genericSetter")
                jitinfo = "&%s_setterinfo" % attr.identifier.name
            return "{ (JSStrictPropertyOp)%s, %s }" % (accessor, jitinfo)

        def specData(attr):
            return (attr.identifier.name, flags(attr), getter(attr),
                    setter(attr))

        return self.generatePrefableArray(
            array, name,
            '  { "%s", 0, %s, %s, %s}',
            '  { 0, 0, 0, JSOP_NULLWRAPPER, JSOP_NULLWRAPPER }',
            'JSPropertySpec',
            PropertyDefiner.getControllingCondition, specData, doIdArrays)

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, doIdArrays):
        if len(array) == 0:
            return ""

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

        return self.generatePrefableArray(
            array, name,
            '  { "%s", %s }',
            '  { 0, JSVAL_VOID }',
            'ConstantSpec',
            PropertyDefiner.getControllingCondition, specData, doIdArrays)

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

    @staticmethod
    def arrayNames():
        return [ "staticMethods", "staticAttrs", "methods", "attrs",
                 "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 CGNativeProperties(CGList):
    def __init__(self, descriptor, properties):
        def generateNativeProperties(name, chrome):
            def check(p):
                return p.hasChromeOnly() if chrome else p.hasNonChromeOnly()

            nativeProps = []
            for array in properties.arrayNames():
                propertyArray = getattr(properties, array)
                if check(propertyArray):
                    if propertyArray.usedForXrays():
                        ids = "%(name)s_ids"
                    else:
                        ids = "nullptr"
                    props = "%(name)s, " + ids + ", %(name)s_specs"
                    props = (props %
                             { 'name': propertyArray.variableName(chrome) })
                else:
                    props = "nullptr, nullptr, nullptr"
                nativeProps.append(CGGeneric(props))
            return CGWrapper(CGIndenter(CGList(nativeProps, ",\n")),
                             pre="static const NativeProperties %s = {\n" % name,
                             post="\n};")

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

    def declare(self):
        return ""

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

    properties should be a PropertyArrays instance.
    """
    def __init__(self, descriptor, properties):
        args = [Argument('JSContext*', 'aCx'),
                Argument('JS::Handle<JSObject*>', 'aGlobal'),
                Argument('JSObject**', 'protoAndIfaceArray')]
        CGAbstractMethod.__init__(self, descriptor, 'CreateInterfaceObjects', 'void', args)
        self.properties = properties
    def definition_body(self):
        protoChain = self.descriptor.prototypeChain
        if len(protoChain) == 1:
            getParentProto = "aCx, JS_GetObjectPrototype(aCx, aGlobal)"
            parentProtoType = "Rooted"
        else:
            parentProtoName = self.descriptor.prototypeChain[-2]
            getParentProto = ("%s::GetProtoObject(aCx, aGlobal)" %
                              toBindingNamespace(parentProtoName))
            parentProtoType = "Handle"

        parentWithInterfaceObject = self.descriptor.interface.parent
        while (parentWithInterfaceObject and
               not parentWithInterfaceObject.hasInterfaceObject()):
            parentWithInterfaceObject = parentWithInterfaceObject.parent
        if parentWithInterfaceObject:
            parentIfaceName = parentWithInterfaceObject.identifier.name
            if self.descriptor.workers:
                parentIfaceName += "_workers"
            getConstructorProto = ("%s::GetConstructorObject(aCx, aGlobal)" %
                                   toBindingNamespace(parentIfaceName))
            constructorProtoType = "Handle"
        else:
            getConstructorProto = "aCx, JS_GetFunctionPrototype(aCx, aGlobal)"
            constructorProtoType = "Rooted"

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

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

        idsToInit = []
        # There is no need to init any IDs in workers, because worker bindings
        # don't have Xrays.
        if not self.descriptor.workers:
            for var in self.properties.arrayNames():
                props = getattr(self.properties, var)
                # We only have non-chrome ids to init if we have no chrome ids.
                if props.hasChromeOnly():
                    idsToInit.append(props.variableName(True))
                if props.hasNonChromeOnly():
                    idsToInit.append(props.variableName(False))
        if len(idsToInit) > 0:
            initIds = CGList(
                [CGGeneric("!InitIds(aCx, %s, %s_ids)" % (varname, varname)) for
                 varname in idsToInit], ' ||\n')
            if len(idsToInit) > 1:
                initIds = CGWrapper(initIds, pre="(", post=")", reindent=True)
            initIds = CGList(
                [CGGeneric("%s_ids[0] == JSID_VOID &&" % idsToInit[0]), initIds],
                "\n")
            initIds = CGWrapper(initIds, pre="if (", post=") {", reindent=True)
            initIds = CGList(
                [initIds,
                 CGGeneric(("  %s_ids[0] = JSID_VOID;\n"
                            "  return;") % idsToInit[0]),
                 CGGeneric("}")],
                "\n")
        else:
            initIds = None

        prefCacheData = []
        for var in self.properties.arrayNames():
            props = getattr(self.properties, var)
            prefCacheData.extend(props.prefCacheData)
        if len(prefCacheData) is not 0:
            prefCacheData = [
                CGGeneric('Preferences::AddBoolVarCache(%s, "%s");' % (ptr, pref)) for
                (pref, ptr) in prefCacheData]
            prefCache = CGWrapper(CGIndenter(CGList(prefCacheData, "\n")),
                                  pre=("static bool sPrefCachesInited = false;\n"
                                       "if (!sPrefCachesInited) {\n"
                                       "  sPrefCachesInited = true;\n"),
                                  post="\n}")
        else:
            prefCache = None
            
        if UseHolderForUnforgeable(self.descriptor):
            createUnforgeableHolder = CGGeneric("""JS::Rooted<JSObject*> unforgeableHolder(aCx,
  JS_NewObjectWithGivenProto(aCx, nullptr, nullptr, nullptr));
if (!unforgeableHolder) {
  return;
}""")
            defineUnforgeables = InitUnforgeablePropertiesOnObject(self.descriptor,
                                                                   "unforgeableHolder",
                                                                   self.properties)
            createUnforgeableHolder = CGList([createUnforgeableHolder,
                                              defineUnforgeables],
                                             "\n")
        else:
            createUnforgeableHolder = None

        getParentProto = ("JS::%s<JSObject*> parentProto(%s);\n" +
                          "if (!parentProto) {\n" +
                          "  return;\n" +
                          "}") % (parentProtoType, getParentProto)

        getConstructorProto = ("JS::%s<JSObject*> constructorProto(%s);\n"
                               "if (!constructorProto) {\n"
                               "  return;\n"
                               "}" % (constructorProtoType, getConstructorProto))

        if (needInterfaceObject and
            self.descriptor.needsConstructHookHolder()):
            constructHookHolder = "&" + CONSTRUCT_HOOK_NAME + "_holder"
        else:
            constructHookHolder = "nullptr"
        if self.descriptor.interface.ctor():
            constructArgs = methodLength(self.descriptor.interface.ctor())
        else:
            constructArgs = 0
        if len(self.descriptor.interface.namedConstructors) > 0:
            namedConstructors = "namedConstructors"
        else:
            namedConstructors = "nullptr"

        if needInterfacePrototypeObject:
            protoClass = "&PrototypeClass.mBase"
            protoCache = "&protoAndIfaceArray[prototypes::id::%s]" % self.descriptor.name
        else:
            protoClass = "nullptr"
            protoCache = "nullptr"
        if needInterfaceObject:
            interfaceClass = "&InterfaceObjectClass.mBase"
            interfaceCache = "&protoAndIfaceArray[constructors::id::%s]" % self.descriptor.name
        else:
            # We don't have slots to store the named constructors.
            assert len(self.descriptor.interface.namedConstructors) == 0
            interfaceClass = "nullptr"
            interfaceCache = "nullptr"

        if self.descriptor.concrete:
            if self.descriptor.proxy:
                domClass = "&Class"
            else:
                domClass = "&Class.mClass"
        else:
            domClass = "nullptr"

        if self.properties.hasNonChromeOnly():
            properties = "&sNativeProperties"
        else:
            properties = "nullptr"
        if self.properties.hasChromeOnly():
            accessCheck = GetAccessCheck(self.descriptor, "aGlobal")
            chromeProperties = accessCheck + " ? &sChromeOnlyNativeProperties : nullptr"
        else:
            chromeProperties = "nullptr"
        call = ("dom::CreateInterfaceObjects(aCx, aGlobal, parentProto,\n"
                "                            %s, %s,\n"
                "                            constructorProto, %s, %s, %d, %s,\n"
                "                            %s,\n"
                "                            %s,\n"
                "                            %s,\n"
                "                            %s,\n"
                "                            %s);" % (
            protoClass, protoCache,
            interfaceClass, constructHookHolder, constructArgs,
            namedConstructors,
            interfaceCache,
            domClass,
            properties,
            chromeProperties,
            '"' + self.descriptor.interface.identifier.name + '"' if needInterfaceObject else "NULL"))
        if UseHolderForUnforgeable(self.descriptor):
            assert needInterfacePrototypeObject
            setUnforgeableHolder = CGGeneric(
                "JSObject* proto = protoAndIfaceArray[prototypes::id::%s];\n"
                "if (proto) {\n"
                "  js::SetReservedSlot(proto, DOM_INTERFACE_PROTO_SLOTS_BASE,\n"
                "                      JS::ObjectValue(*unforgeableHolder));\n"
                "}" % self.descriptor.name)
        else:
            setUnforgeableHolder = None
        functionBody = CGList(
            [CGGeneric(getParentProto), CGGeneric(getConstructorProto), initIds,
             prefCache, createUnforgeableHolder, CGGeneric(call), setUnforgeableHolder],
            "\n\n")
        return CGIndenter(functionBody).define()

class CGGetPerInterfaceObject(CGAbstractMethod):
    """
    A method for getting a per-interface object (a prototype object or interface
    constructor object).
    """
    def __init__(self, descriptor, name, idPrefix=""):
        args = [Argument('JSContext*', 'aCx'),
                Argument('JS::Handle<JSObject*>', 'aGlobal')]
        CGAbstractMethod.__init__(self, descriptor, name,
                                  'JS::Handle<JSObject*>', args, inline=True)
        self.id = idPrefix + "id::" + self.descriptor.name
    def definition_body(self):
        return ("""

  /* Make sure our global is sane.  Hopefully we can remove this sometime */
  if (!(js::GetObjectClass(aGlobal)->flags & JSCLASS_DOM_GLOBAL)) {
    return JS::NullPtr();
  }
  /* Check to see whether the interface objects are already installed */
  JSObject** protoAndIfaceArray = GetProtoAndIfaceArray(aGlobal);
  if (!protoAndIfaceArray[%s]) {
    CreateInterfaceObjects(aCx, aGlobal, protoAndIfaceArray);
  }

  /* The object might _still_ be null, but that's OK */
  return JS::Handle<JSObject*>::fromMarkedLocation(&protoAndIfaceArray[%s]);""" %
                (self.id, self.id))

class CGGetProtoObjectMethod(CGGetPerInterfaceObject):
    """
    A method for getting the interface prototype object.
    """
    def __init__(self, descriptor):
        CGGetPerInterfaceObject.__init__(self, descriptor, "GetProtoObject",
                                         "prototypes::")
    def definition_body(self):
        return """
  /* Get the interface prototype object for this class.  This will create the
     object as needed. */""" + CGGetPerInterfaceObject.definition_body(self)

class CGGetConstructorObjectMethod(CGGetPerInterfaceObject):
    """
    A method for getting the interface constructor object.
    """
    def __init__(self, descriptor):
        CGGetPerInterfaceObject.__init__(self, descriptor, "GetConstructorObject",
                                         "constructors::")
    def definition_body(self):
        return """
  /* Get the interface object for this class.  This will create the object as
     needed. */""" + CGGetPerInterfaceObject.definition_body(self)

class CGDefineDOMInterfaceMethod(CGAbstractMethod):
    """
    A method for resolve hooks to try to lazily define the interface object for
    a given interface.
    """
    def __init__(self, descriptor):
        args = [Argument('JSContext*', 'aCx'),
                Argument('JS::Handle<JSObject*>', 'aGlobal'),
                Argument('JS::Handle<jsid>', 'id'),
                Argument('bool*', 'aEnabled')]
        CGAbstractMethod.__init__(self, descriptor, 'DefineDOMInterface', 'JSObject*', args)

    def declare(self):
        if self.descriptor.workers:
            return ''
        return CGAbstractMethod.declare(self)

    def define(self):
        if self.descriptor.workers:
            return ''
        return CGAbstractMethod.define(self)

    def definition_body(self):
        if len(self.descriptor.interface.namedConstructors) > 0:
            getConstructor = """  JSObject* interfaceObject = GetConstructorObject(aCx, aGlobal);
  if (!interfaceObject) {
    return nullptr;
  }
  for (unsigned slot = DOM_INTERFACE_SLOTS_BASE; slot < JSCLASS_RESERVED_SLOTS(&InterfaceObjectClass.mBase); ++slot) {
    JSObject* constructor = &js::GetReservedSlot(interfaceObject, slot).toObject();
    if (JS_GetFunctionId(JS_GetObjectFunction(constructor)) == JSID_TO_STRING(id)) {
      return constructor;
    }
  }
  return interfaceObject;"""
        else:
            getConstructor = "  return GetConstructorObject(aCx, aGlobal);"
        return ("""  *aEnabled = true;

""" + getConstructor)

class CGPrefEnabledNative(CGAbstractMethod):
    """
    A method for testing whether the preference controlling this
    interface is enabled. This delegates to PrefEnabled() on the
    wrapped class. The interface should only be visible on the global
    if the method returns true.
    """
    def __init__(self, descriptor):
        CGAbstractMethod.__init__(self, descriptor, 'PrefEnabled', 'bool', [])

    def definition_body(self):
        return "  return %s::PrefEnabled();" % self.descriptor.nativeType

class CGPrefEnabled(CGAbstractMethod):
    """
    A method for testing whether the preference controlling this
    interface is enabled. This generates code in the binding to
    check the given preference. The interface should only be visible
    on the global if the pref is true.
    """
    def __init__(self, descriptor):
        CGAbstractMethod.__init__(self, descriptor, 'PrefEnabled', 'bool', [])

    def definition_body(self):
        pref = self.descriptor.interface.getExtendedAttribute("Pref")
        assert isinstance(pref, list) and len(pref) == 1
        return "  return Preferences::GetBool(\"%s\");" % pref[0]

class CGIsMethod(CGAbstractMethod):
    def __init__(self, descriptor):
        args = [Argument('JSObject*', 'obj')]
        CGAbstractMethod.__init__(self, descriptor, 'Is', 'bool', args)

    def definition_body(self):
        # Non-proxy implementation would check
        #   js::GetObjectJSClass(obj) == &Class.mBase
        return """  return IsProxy(obj);"""

def CreateBindingJSObject(descriptor, properties, parent):
    # When we have unforgeable properties, we're going to define them
    # on our object, so we have to root it when we create it, so it
    # won't suddenly die while defining the unforgeables.
    needRoot = (properties.unforgeableAttrs.hasNonChromeOnly() or
                properties.unforgeableAttrs.hasChromeOnly())
    if needRoot:
        objDecl = "  JS::Rooted<JSObject*> obj(aCx);\n"
    else:
        objDecl = "  JSObject *obj;\n"
    if descriptor.proxy:
        create = """  obj = NewProxyObject(aCx, DOMProxyHandler::getInstance(),
                       JS::PrivateValue(aObject), proto, %s);
  if (!obj) {
    return NULL;
  }

"""
        if descriptor.interface.getExtendedAttribute('OverrideBuiltins'):
            create += """  js::SetProxyExtra(obj, JSPROXYSLOT_EXPANDO,
                    JS::PrivateValue(&aObject->mExpandoAndGeneration));

"""
    else:
        create = """  obj = JS_NewObject(aCx, &Class.mBase, proto, %s);
  if (!obj) {
    return NULL;
  }

  js::SetReservedSlot(obj, DOM_OBJECT_SLOT, PRIVATE_TO_JSVAL(aObject));
"""
    create = objDecl + create

    if descriptor.nativeOwnership in ['refcounted', 'nsisupports']:
        create += """  NS_ADDREF(aObject);
"""
    else:
        assert descriptor.nativeOwnership == 'owned'
        create += """  // Make sure the native objects inherit from NonRefcountedDOMObject so that we
  // log their ctor and dtor.
  MustInheritFromNonRefcountedDOMObject(aObject);
  *aTookOwnership = true;
"""
    return create % parent

def GetAccessCheck(descriptor, object):
    """
    object is the name of a JSObject*

    returns a string
    """
    if descriptor.workers:
        accessCheck = "mozilla::dom::workers::GetWorkerPrivateFromContext(aCx)->IsChromeWorker()"
    else:
        accessCheck = "xpc::AccessCheck::isChrome(%s)" % object
    return accessCheck

def InitUnforgeablePropertiesOnObject(descriptor, obj, properties, failureReturnValue=""):
    """
    properties is a PropertyArrays instance
    """
    failureReturn = "return"
    if len(failureReturnValue) > 0:
        failureReturn += " " + failureReturnValue
    failureReturn += ";"
        
    defineUnforgeables = ("if (!DefineUnforgeableAttributes(aCx, " + obj + ", %s)) {\n"
                          "  " + failureReturn + "\n"
                          "}")

    unforgeableAttrs = properties.unforgeableAttrs
    unforgeables = []
    if unforgeableAttrs.hasNonChromeOnly():
        unforgeables.append(CGGeneric(defineUnforgeables %
                                      unforgeableAttrs.variableName(False)))
    if unforgeableAttrs.hasChromeOnly():
        unforgeables.append(
            CGIfWrapper(CGGeneric(defineUnforgeables %
                                  unforgeableAttrs.variableName(True)),
                        GetAccessCheck(descriptor, obj)))
    return CGList(unforgeables, "\n")

def InitUnforgeableProperties(descriptor, properties):
    """
    properties is a PropertyArrays instance
    """
    unforgeableAttrs = properties.unforgeableAttrs
    if not unforgeableAttrs.hasNonChromeOnly() and not unforgeableAttrs.hasChromeOnly():
        return ""

    if descriptor.proxy:
        unforgeableProperties = CGGeneric(
            "// Unforgeable properties on proxy-based bindings are stored in an object held\n"
            "// by the interface prototype object.\n")
    else:
        unforgeableProperties = CGWrapper(
            InitUnforgeablePropertiesOnObject(descriptor, "obj", properties, "nullptr"),
            pre=(
            "// Important: do unforgeable property setup after we have handed\n"
            "// over ownership of the C++ object to obj as needed, so that if\n"
            "// we fail and it ends up GCed it won't have problems in the\n"
            "// finalizer trying to drop its ownership of the C++ object.\n"))
    return CGIndenter(CGWrapper(unforgeableProperties, pre="\n", post="\n")).define()

def AssertInheritanceChain(descriptor):
    asserts = ""
    iface = descriptor.interface
    while iface:
        desc = descriptor.getDescriptor(iface.identifier.name)
        asserts += (
            "  MOZ_ASSERT(static_cast<%s*>(aObject) == \n"
            "             reinterpret_cast<%s*>(aObject));\n" %
            (desc.nativeType, desc.nativeType))
        iface = iface.parent
    if descriptor.nativeOwnership == 'nsisupports':
        asserts += (
            "  MOZ_ASSERT(ToSupports(aObject) == \n"
            "             reinterpret_cast<nsISupports*>(aObject));\n")
    return asserts

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

    properties should be a PropertyArrays instance.
    """
    def __init__(self, descriptor, properties):
        assert descriptor.interface.hasInterfacePrototypeObject()
        args = [Argument('JSContext*', 'aCx'),
                Argument('JS::Handle<JSObject*>', 'aScope'),
                Argument(descriptor.nativeType + '*', 'aObject'),
                Argument('nsWrapperCache*', 'aCache')]
        CGAbstractMethod.__init__(self, descriptor, 'Wrap', 'JSObject*', args)
        self.properties = properties

    def definition_body(self):
        if self.descriptor.workers:
            return """  return aObject->GetJSObject();"""

        if self.descriptor.nativeOwnership == 'nsisupports':
            assertISupportsInheritance = (
                '  MOZ_ASSERT(reinterpret_cast<void*>(aObject) != aCache,\n'
                '             "nsISupports must be on our primary inheritance chain");\n')
        else:
            assertISupportsInheritance = ""
        return """%s
%s
  JS::Rooted<JSObject*> parent(aCx,
    GetRealParentObject(aObject,
                        WrapNativeParent(aCx, aScope, aObject->GetParentObject())));
  if (!parent) {
    return NULL;
  }

  // That might have ended up wrapping us already, due to the wonders
  // of XBL.  Check for that, and bail out as needed.  Scope so we don't
  // collide with the "obj" we declare in CreateBindingJSObject.
  {
    JSObject* obj = aCache->GetWrapper();
    if (obj) {
      return obj;
    }
  }

  JSAutoCompartment ac(aCx, parent);
  JS::Rooted<JSObject*> global(aCx, JS_GetGlobalForObject(aCx, parent));
  JS::Handle<JSObject*> proto = GetProtoObject(aCx, global);
  if (!proto) {
    return NULL;
  }

%s
%s
  aCache->SetWrapper(obj);

  return obj;""" % (AssertInheritanceChain(self.descriptor),
                    assertISupportsInheritance,
                    CreateBindingJSObject(self.descriptor, self.properties,
                                          "parent"),
                    InitUnforgeableProperties(self.descriptor, self.properties))

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('JS::Handle<JSObject*>', 'aScope'),
                Argument('T*', 'aObject')]
        CGAbstractMethod.__init__(self, descriptor, 'Wrap', 'JSObject*', args, inline=True, templateArgs=["class T"])

    def definition_body(self):
        return "  return Wrap(aCx, aScope, aObject, aObject);"

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

    properties should be a PropertyArrays instance.
    """
    def __init__(self, descriptor, properties):
        # XXX can we wrap if we don't have an interface prototype object?
        assert descriptor.interface.hasInterfacePrototypeObject()
        args = [Argument('JSContext*', 'aCx'),
                Argument('JS::Handle<JSObject*>', 'aScope'),
                Argument(descriptor.nativeType + '*', 'aObject')]
        if descriptor.nativeOwnership == 'owned':
            args.append(Argument('bool*', 'aTookOwnership'))
        CGAbstractMethod.__init__(self, descriptor, 'Wrap', 'JSObject*', args)
        self.properties = properties

    def definition_body(self):
        return """%s
  JS::Rooted<JSObject*> global(aCx, JS_GetGlobalForObject(aCx, aScope));
  JS::Handle<JSObject*> proto = GetProtoObject(aCx, global);
  if (!proto) {
    return NULL;
  }

%s
%s
  return obj;""" % (AssertInheritanceChain(self.descriptor),
                    CreateBindingJSObject(self.descriptor, self.properties,
                                          "global"),
                    InitUnforgeableProperties(self.descriptor, self.properties))

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: 'D',
    IDLType.Tags.double: 'D'
}

def numericValue(t, v):
    if (t == IDLType.Tags.unrestricted_double or
        t == IDLType.Tags.unrestricted_float):
        if v == float("inf"):
            return "MOZ_DOUBLE_POSITIVE_INFINITY()"
        if v == float("-inf"):
            return "MOZ_DOUBLE_NEGATIVE_INFINITY()"
        if math.isnan(v):
            return "MOZ_DOUBLE_NaN()"
    return "%s%s" % (v, numericSuffixes[t])

class CastableObjectUnwrapper():
    """
    A class for unwrapping an object named by the "source" argument
    based on the passed-in descriptor and storing it in a variable
    called by the name in the "target" argument.

    codeOnFailure is the code to run if unwrapping fails.
    """
    def __init__(self, descriptor, source, target, codeOnFailure):
        self.substitution = { "type" : descriptor.nativeType,
                              "protoID" : "prototypes::id::" + descriptor.name,
                              "source" : source,
                              "target" : target,
                              "codeOnFailure" : CGIndenter(CGGeneric(codeOnFailure), 4).define() }
        if descriptor.hasXPConnectImpls:
            # We don't use xpc_qsUnwrapThis because it will always throw on
            # unwrap failure, whereas we want to control whether we throw or
            # not.
            self.substitution["codeOnFailure"] = CGIndenter(CGGeneric(string.Template(
                "${type} *objPtr;\n"
                "xpc_qsSelfRef objRef;\n"
                "JS::Rooted<JS::Value> val(cx, JS::ObjectValue(*${source}));\n"
                "nsresult rv = xpc_qsUnwrapArg<${type}>(cx, val, &objPtr, &objRef.ptr, val.address());\n"
                "if (NS_FAILED(rv)) {\n"
                "${codeOnFailure}\n"
                "}\n"
                "// We should be castable!\n"
                "MOZ_ASSERT(!objRef.ptr);\n"
                "// We should have an object, too!\n"
                "MOZ_ASSERT(objPtr);\n"
                "${target} = objPtr;").substitute(self.substitution)), 4).define()

    def __str__(self):
        return string.Template(
"""{
  nsresult rv = UnwrapObject<${protoID}, ${type}>(cx, ${source}, ${target});
  if (NS_FAILED(rv)) {
${codeOnFailure}
  }
}""").substitute(self.substitution)

class FailureFatalCastableObjectUnwrapper(CastableObjectUnwrapper):
    """
    As CastableObjectUnwrapper, but defaulting to throwing if unwrapping fails
    """
    def __init__(self, descriptor, source, target, exceptionCode):
        CastableObjectUnwrapper.__init__(
            self, descriptor, source, target,
            'ThrowErrorMessage(cx, MSG_DOES_NOT_IMPLEMENT_INTERFACE, "%s");\n'
            '%s' % (descriptor.name, exceptionCode))

class CallbackObjectUnwrapper:
    """
    A class for unwrapping objects implemented in JS.

    |source| is the JSObject we want to use in native code.
    |target| is an nsCOMPtr of the appropriate type in which we store the result.
    """
    def __init__(self, descriptor, source, target, exceptionCode,
                 codeOnFailure=None):
        if codeOnFailure is None:
            codeOnFailure = (
                'ThrowErrorMessage(cx, MSG_DOES_NOT_IMPLEMENT_INTERFACE, "%s");\n'
                '%s' % (descriptor.name, exceptionCode))
        self.descriptor = descriptor
        self.substitution = { "nativeType" : descriptor.nativeType,
                              "source" : source,
                              "target" : target,
                              "codeOnFailure" : CGIndenter(CGGeneric(codeOnFailure)).define() }

    def __str__(self):
        checkObjectType = CGIfWrapper(
            CGGeneric(self.substitution["codeOnFailure"]),
            "!IsConvertibleToCallbackInterface(cx, %(source)s)" %
            self.substitution).define() + "\n\n"
        if self.descriptor.workers:
            return checkObjectType + string.Template(
                "${target} = ${source};"
                ).substitute(self.substitution)

        return checkObjectType + string.Template(
            """nsresult rv;
XPCCallContext ccx(JS_CALLER, cx);
if (!ccx.IsValid()) {
  rv = NS_ERROR_XPC_BAD_CONVERT_JS;
${codeOnFailure}
}

nsISupports* supp = nullptr;
if (XPCConvert::GetISupportsFromJSObject(${source}, &supp)) {
  nsCOMPtr<nsIXPConnectWrappedNative> xpcwn = do_QueryInterface(supp);
  if (xpcwn) {
    supp = xpcwn->Native();
  }
}

const nsIID& iid = NS_GET_IID(${nativeType});
nsRefPtr<nsXPCWrappedJS> wrappedJS;
rv = nsXPCWrappedJS::GetNewOrUsed(ccx, ${source}, iid,
                                  supp, getter_AddRefs(wrappedJS));
if (NS_FAILED(rv) || !wrappedJS) {
${codeOnFailure}
}

// Use a temp nsCOMPtr for the null-check, because ${target} might be
// OwningNonNull, not an nsCOMPtr.
nsCOMPtr<${nativeType}> tmp = do_QueryObject(wrappedJS.get());
if (!tmp) {
${codeOnFailure}
}
${target} = tmp.forget();""").substitute(self.substitution)

# 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 getJSToNativeConversionTemplate(type, descriptorProvider, failureCode=None,
                                    isDefinitelyObject=False,
                                    isMember=False,
                                    isOptional=False,
                                    invalidEnumValueFatal=True,
                                    defaultValue=None,
                                    treatNullAs="Default",
                                    treatUndefinedAs="Default",
                                    isEnforceRange=False,
                                    isClamp=False,
                                    isNullOrUndefined=False,
                                    exceptionCode=None,
                                    lenientFloatCode=None,
                                    allowTreatNonCallableAsNull=False,
                                    isCallbackReturnValue=False):
    """
    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 know the value
    isObject() and we have no need to recheck that.

    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" or
    "Variadic" to indicate that the conversion is for something that is a
    dictionary member or a variadic argument respectively.

    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 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]
    extended attributes on nullable callback functions will be honored.

    If isCallbackReturnValue is true, 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.

    The return value from this function is a tuple consisting of four things:

    1)  A string representing the conversion code.  This will have template
        substitution performed on it as follows:

          ${val} replaced by an expression for the JS::Value in question
          ${valPtr} is a pointer to the JS::Value in question
          ${valHandle} is a handle to the JS::Value in question
          ${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.

    2)  A CGThing representing the native C++ type we're converting to
        (declType).  This is allowed to be None if the conversion code is
        supposed to be used as-is.
    3)  A CGThing representing the type of a "holder" (holderType) which will
        hold a possible reference to the C++ thing whose type we returned in #1,
        or None if no such holder is needed.
    4)  A boolean indicating whether the caller has to do optional-argument handling.
        This will only be true if isOptional is true 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.

    ${declName} must be in scope before the generated code is entered.

    If holderType is not None then ${holderName} must be in scope
    before the generated code is entered.
    """
    # 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

    # 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;"
    # We often want exceptionCode to be indented, since it often appears in an
    # if body.
    exceptionCodeIndented = CGIndenter(CGGeneric(exceptionCode))

    # Helper functions for dealing with failures due to the JS value being the
    # wrong type of value
    def onFailureNotAnObject(failureCode):
        return CGWrapper(CGGeneric(
                failureCode or
                ('ThrowErrorMessage(cx, MSG_NOT_OBJECT);\n'
                 '%s' % exceptionCode)), post="\n")
    def onFailureBadType(failureCode, typeName):
        return CGWrapper(CGGeneric(
                failureCode or
                ('ThrowErrorMessage(cx, MSG_DOES_NOT_IMPLEMENT_INTERFACE, "%s");'
                 '%s' % (typeName, exceptionCode))), post="\n")
    def onFailureNotCallable(failureCode):
        return CGWrapper(CGGeneric(
                failureCode or
                ('ThrowErrorMessage(cx, MSG_NOT_CALLABLE);\n'
                 '%s' % exceptionCode)), post="\n")

    # 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
        return CGWrapper(
            CGIndenter(CGGeneric(template)),
            pre="if (${haveValue}) {\n",
            post=("\n"
                  "} else {\n"
                  "%s;\n"
                  "}" %
                  CGIndenter(CGGeneric(setDefault)).define())).define()

    # A helper function for handling null default values.  Much like
    # handleDefault, but checks that the default value, if it exists, is null.
    def handleDefaultNull(template, codeToSetNull):
        if (defaultValue is not None and
            not isinstance(defaultValue, IDLNullValue)):
            raise TypeError("Can't handle non-null default value here")
        return handleDefault(template, codeToSetNull)

    # A helper function for wrapping up the template body for
    # possibly-nullable objecty stuff
    def wrapObjectTemplate(templateBody, type, codeToSetNull, failureCode=None):
        if isNullOrUndefined:
            assert 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 "%s;" % codeToSetNull

        if not isDefinitelyObject:
            # Handle the non-object cases by wrapping up the whole
            # thing in an if cascade.
            templateBody = (
                "if (${val}.isObject()) {\n" +
                CGIndenter(CGGeneric(templateBody)).define() + "\n")
            if type.nullable():
                templateBody += (
                    "} else if (${val}.isNullOrUndefined()) {\n"
                    "%s;\n" % CGIndenter(CGGeneric(codeToSetNull)).define())
            templateBody += (
                "} else {\n" +
                CGIndenter(onFailureNotAnObject(failureCode)).define() +
                "}")
            if type.nullable():
                templateBody = handleDefaultNull(templateBody, codeToSetNull)
            else:
                assert(defaultValue is None)

        return templateBody

    # A helper function for converting things that look like JSObject*
    # when nullable and JSObject& when not nullable.
    def handleJSObjectType(type, isMember, failureCode):
        if type.nullable():
            declType = CGGeneric("LazyRootedObject")
        else:
            declType = CGGeneric("NonNullLazyRootedObject")

        # If cx is null then LazyRootedObject will not be
        # constructed and behave as nullptr.
        templateBody = "${declName}.construct(cx, &${val}.toObject());"

        # Cast of nullptr to (JSObject*) is required for template deduction.
        setToNullCode = "${declName}.construct(cx, static_cast<JSObject*>(nullptr));"

        if isMember == "Dictionary":
            # If cx is null then LazyRootedObject will not be
            # constructed and behave as nullptr.
            templateBody = CGIfWrapper(CGGeneric(templateBody), "cx").define()
            setToNullCode = CGIfWrapper(CGGeneric(setToNullCode), "cx").define()

        template = wrapObjectTemplate(templateBody, type, setToNullCode,
                                      failureCode)

        return (template, declType, None, isOptional)


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

    if type.isArray():
        raise TypeError("Can't handle array arguments yet")

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

        if failureCode is None:
            notSequence = ("ThrowErrorMessage(cx, MSG_NOT_SEQUENCE);\n"
                           "%s" % 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 nsAutoTarray to the right size
        # will memmove its elements, but nsAutoTArrays 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 or isOptional or nullable or isCallbackReturnValue:
            sequenceClass = "Sequence"
        else:
            sequenceClass = "AutoSequence"

        (elementTemplate, elementDeclType,
         elementHolderType, dealWithOptional) = getJSToNativeConversionTemplate(
            elementType, descriptorProvider, isMember=True,
            exceptionCode=exceptionCode, lenientFloatCode=lenientFloatCode,
            isCallbackReturnValue=isCallbackReturnValue)
        if dealWithOptional:
            raise TypeError("Shouldn't have optional things in sequences")
        if elementHolderType is not None:
            raise TypeError("Shouldn't need holders for sequences")

        typeName = CGTemplatedType(sequenceClass, elementDeclType)
        sequenceType = typeName.define()
        if nullable:
            typeName = CGTemplatedType("Nullable", typeName)
            arrayRef = "${declName}.SetValue()"
        else:
            arrayRef = "${declName}"

        # NOTE: Keep this in sync with variadic conversions as needed
        templateBody = ("""JS::Rooted<JSObject*> seq(cx, &${val}.toObject());\n
if (!IsArrayLike(cx, seq)) {
%s
}
uint32_t length;
// JS_GetArrayLength actually works on all objects
if (!JS_GetArrayLength(cx, seq, &length)) {
%s
}
%s &arr = %s;
if (!arr.SetCapacity(length)) {
  JS_ReportOutOfMemory(cx);
%s
}
for (uint32_t i = 0; i < length; ++i) {
  JS::Rooted<JS::Value> temp(cx);
  if (!JS_GetElement(cx, seq, i, temp.address())) {
%s
  }
  %s& slot = *arr.AppendElement();
""" % (CGIndenter(CGGeneric(notSequence)).define(),
       exceptionCodeIndented.define(),
       sequenceType,
       arrayRef,
       exceptionCodeIndented.define(),
       CGIndenter(exceptionCodeIndented).define(),
       elementDeclType.define()))

        templateBody += CGIndenter(CGGeneric(
                string.Template(elementTemplate).substitute(
                    {
                        "val" : "temp",
                        "valPtr": "temp.address()",
                        "valHandle": "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",
                        }
                    ))).define()

        templateBody += "\n}"
        templateBody = wrapObjectTemplate(templateBody, type,
                                          "${declName}.SetNull()")
        return (templateBody, typeName, None, isOptional)

    if type.isUnion():
        if isMember:
            raise TypeError("Can't handle unions as members, we have a "
                            "holderType")
        nullable = type.nullable();
        if nullable:
            type = type.inner

        assert(defaultValue is None or
               (isinstance(defaultValue, IDLNullValue) and nullable))

        unionArgumentObj = "${holderName}"
        if isOptional or nullable:
            unionArgumentObj += ".ref()"

        memberTypes = type.flatMemberTypes
        names = []

        interfaceMemberTypes = filter(lambda t: t.isNonCallbackInterface(), memberTypes)
        if len(interfaceMemberTypes) > 0:
            interfaceObject = []
            for memberType in interfaceMemberTypes:
                if type.isGeckoInterface():
                    name = memberType.inner.identifier.name
                else:
                    name = memberType.name
                interfaceObject.append(CGGeneric("(failed = !%s.TrySetTo%s(cx, ${valHandle}, ${valPtr}, tryNext)) || !tryNext" % (unionArgumentObj, name)))
                names.append(name)
            interfaceObject = CGWrapper(CGList(interfaceObject, " ||\n"), pre="done = ", post=";\n", reindent=True)
        else:
            interfaceObject = None

        arrayObjectMemberTypes = filter(lambda t: t.isArray() or t.isSequence(), memberTypes)
        if len(arrayObjectMemberTypes) > 0:
            assert len(arrayObjectMemberTypes) == 1
            memberType = arrayObjectMemberTypes[0]
            name = memberType.name
            arrayObject = CGGeneric("done = (failed = !%s.TrySetTo%s(cx, ${valHandle}, ${valPtr}, tryNext)) || !tryNext;" % (unionArgumentObj, name))
            arrayObject = CGIfWrapper(arrayObject, "IsArrayLike(cx, &argObj)")
            names.append(name)
        else:
            arrayObject = None

        dateObjectMemberTypes = filter(lambda t: t.isDate(), memberTypes)
        if len(dateObjectMemberTypes) > 0:
            assert len(dateObjectMemberTypes) == 1
            memberType = dateObjectMemberTypes[0]
            name = memberType.name
            dateObject = CGGeneric("%s.SetTo%s(cx, ${val}, ${valPtr});\n"
                                   "done = true;" % (unionArgumentObj, name))
            dateObject = CGIfWrapper(dateObject, "JS_ObjectIsDate(cx, &argObj)");
            names.append(name)
        else:
            dateObject = None

        callbackMemberTypes = filter(lambda t: t.isCallback() or t.isCallbackInterface(), memberTypes)
        if len(callbackMemberTypes) > 0:
            assert len(callbackMemberTypes) == 1
            memberType = callbackMemberTypes[0]
            name = memberType.name
            callbackObject = CGGeneric("done = (failed = !%s.TrySetTo%s(cx, ${valHandle}, ${valPtr}, tryNext)) || !tryNext;" % (unionArgumentObj, name))
            names.append(name)
        else:
            callbackObject = None

        dictionaryMemberTypes = filter(lambda t: t.isDictionary(), memberTypes)
        if len(dictionaryMemberTypes) > 0:
            raise TypeError("No support for unwrapping dictionaries as member "
                            "of a union")
        else:
            dictionaryObject = None

        objectMemberTypes = filter(lambda t: t.isObject(), memberTypes)
        if len(objectMemberTypes) > 0:
            object = CGGeneric("%s.SetToObject(cx, &argObj);\n"
                               "done = true;" % unionArgumentObj)
        else:
            object = None

        hasObjectTypes = interfaceObject or arrayObject or dateObject or callbackObject or dictionaryObject or object
        if hasObjectTypes:
            # "object" is not distinguishable from other types
            assert not object or not (interfaceObject or arrayObject or dateObject or callbackObject or dictionaryObject)
            if arrayObject or dateObject or callbackObject or dictionaryObject:
                # An object can be both an array object and a callback or
                # dictionary, but we shouldn't have both in the union's members
                # because they are not distinguishable.
                assert not (arrayObject and callbackObject)
                assert not (arrayObject and dictionaryObject)
                assert not (dictionaryObject and callbackObject)
                templateBody = CGList([arrayObject, dateObject, callbackObject,
                                       dictionaryObject], " else ")
            else:
                templateBody = None
            if interfaceObject:
                assert not object
                if templateBody:
                    templateBody = CGIfWrapper(templateBody, "!done")
                templateBody = CGList([interfaceObject, templateBody], "\n")
            else:
                templateBody = CGList([templateBody, object], "\n")

            if any([arrayObject, dateObject, callbackObject, dictionaryObject,
                    object]):
                templateBody.prepend(CGGeneric("JSObject& argObj = ${val}.toObject();"))
            templateBody = CGIfWrapper(templateBody, "${val}.isObject()")
        else:
            templateBody = CGGeneric()

        otherMemberTypes = filter(lambda t: t.isString() or t.isEnum(),
                                  memberTypes)
        otherMemberTypes.extend(t for t in memberTypes if t.isPrimitive())
        if len(otherMemberTypes) > 0:
            assert len(otherMemberTypes) == 1
            memberType = otherMemberTypes[0]
            if memberType.isEnum():
                name = memberType.inner.identifier.name
            else:
                name = memberType.name
            other = CGGeneric("done = (failed = !%s.TrySetTo%s(cx, ${valHandle}, ${valPtr}, tryNext)) || !tryNext;" % (unionArgumentObj, name))
            names.append(name)
            if hasObjectTypes:
                other = CGWrapper(CGIndenter(other), "{\n", post="\n}")
                if object:
                    join = " else "
                else:
                    other = CGWrapper(other, pre="if (!done) ")
                    join = "\n"
                templateBody = CGList([templateBody, other], join)
        else:
            other = None

        templateBody = CGWrapper(templateBody, pre="bool done = false, failed = false, tryNext;\n")
        throw = CGGeneric("if (failed) {\n"
                          "%s\n"
                          "}\n"
                          "if (!done) {\n"
                          "  ThrowErrorMessage(cx, MSG_NOT_IN_UNION, \"%s\");\n"
                          "%s\n"
                          "}" % (exceptionCodeIndented.define(),
                                 ", ".join(names),
                                 exceptionCodeIndented.define()))
        templateBody = CGWrapper(CGIndenter(CGList([templateBody, throw], "\n")), pre="{\n", post="\n}")

        typeName = type.name
        argumentTypeName = typeName + "Argument"
        if nullable:
            typeName = "Nullable<" + typeName + " >"

        def handleNull(templateBody, setToNullVar, extraConditionForNull=""):
            null = CGGeneric("if (%s${val}.isNullOrUndefined()) {\n"
                             "  %s.SetNull();\n"
                             "}" % (extraConditionForNull, setToNullVar))
            templateBody = CGWrapper(CGIndenter(templateBody), pre="{\n", post="\n}")
            return CGList([null, templateBody], " else ")

        if type.hasNullableType:
            templateBody = handleNull(templateBody, unionArgumentObj)

        declType = CGGeneric(typeName)
        holderType = CGGeneric(argumentTypeName)
        if isOptional:
            mutableDecl = "${declName}.Value()"
            declType = CGTemplatedType("Optional", declType)
            holderType = CGTemplatedType("Maybe", holderType)
            constructDecl = CGGeneric("${declName}.Construct();")
            if nullable:
                constructHolder = CGGeneric("${holderName}.construct(%s.SetValue());" % mutableDecl)
            else:
                constructHolder = CGGeneric("${holderName}.construct(${declName}.Value());")
        else:
            mutableDecl = "${declName}"
            constructDecl = None
            if nullable:
                holderType = CGTemplatedType("Maybe", holderType)
                constructHolder = CGGeneric("${holderName}.construct(%s.SetValue());" % mutableDecl)
            else:
                constructHolder = CGWrapper(holderType, post=" ${holderName}(${declName});")
                holderType = None

        templateBody = CGList([constructHolder, templateBody], "\n")
        if nullable:
            if defaultValue:
                assert(isinstance(defaultValue, IDLNullValue))
                valueMissing = "!(${haveValue}) || "
            else:
                valueMissing = ""
            templateBody = handleNull(templateBody, mutableDecl,
                                      extraConditionForNull=valueMissing)
        templateBody = CGList([constructDecl, templateBody], "\n")

        return templateBody.define(), declType, holderType, False

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

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

        if (descriptor.interface.isCallback() and
            descriptor.interface.identifier.name != "EventListener"):
            if descriptor.workers:
                return handleJSObjectType(type, isMember, failureCode)

            name = descriptor.interface.identifier.name
            if type.nullable() or isCallbackReturnValue:
                declType = CGGeneric("nsRefPtr<%s>" % name);
            else:
                declType = CGGeneric("OwningNonNull<%s>" % name)
            conversion = (
                "  ${declName} = new %s(&${val}.toObject());\n" % name)

            template = wrapObjectTemplate(conversion, type,
                                          "${declName} = nullptr",
                                          failureCode)
            return (template, declType, None, 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 nsRefPtr or raw pointer for callback return values to make
        # them easier to return.
        argIsPointer = (type.nullable() or type.unroll().inner.isExternal() or
                        isCallbackReturnValue)

        # Sequences and non-worker callbacks have to hold a strong ref to the
        # thing being passed down.
        forceOwningType = (descriptor.interface.isCallback() and
                           not descriptor.workers) or isMember

        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 = "nsRefPtr<" + typeName + ">"
            else:
                declType = typePtr
        else:
            if forceOwningType:
                declType = "OwningNonNull<" + typeName + ">"
            else:
                declType = "NonNull<" + typeName + ">"

        templateBody = ""
        if descriptor.interface.isCallback():
            templateBody += str(CallbackObjectUnwrapper(
                    descriptor,
                    "&${val}.toObject()",
                    "${declName}",
                    exceptionCode,
                    codeOnFailure=failureCode))
        elif not descriptor.skipGen and not descriptor.interface.isConsequential() and not descriptor.interface.isExternal():
            if failureCode is not None:
                templateBody += str(CastableObjectUnwrapper(
                        descriptor,
                        "&${val}.toObject()",
                        "${declName}",
                        failureCode))
            else:
                templateBody += str(FailureFatalCastableObjectUnwrapper(
                        descriptor,
                        "&${val}.toObject()",
                        "${declName}",
                        exceptionCode))
        elif descriptor.workers:
            return handleJSObjectType(type, isMember, failureCode)
        else:
            # Either external, or new-binding non-castable.  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(nsRefPtr) 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 += "nsRefPtr<" + typeName + "> ${holderName};\n"
            else:
                holderType = "nsRefPtr<" + typeName + ">"
            templateBody += (
                "JS::Rooted<JS::Value> tmpVal(cx, ${val});\n" +
                typePtr + " tmp;\n"
                "if (NS_FAILED(xpc_qsUnwrapArg<" + typeName + ">(cx, ${val}, &tmp, static_cast<" + typeName + "**>(getter_AddRefs(${holderName})), tmpVal.address()))) {\n")
            templateBody += CGIndenter(onFailureBadType(failureCode,
                                                        descriptor.interface.identifier.name)).define()
            templateBody += ("}\n"
                "MOZ_ASSERT(tmp);\n")

            if not isDefinitelyObject and not forceOwningType:
                # Our tmpVal will go out of scope, so we can't rely on it
                # for rooting
                templateBody += (
                    "if (tmpVal != ${val} && !${holderName}) {\n"
                    "  // We have to have a strong ref, because we got this off\n"
                    "  // some random object that might get GCed\n"
                    "  ${holderName} = tmp;\n"
                    "}\n")

            # And store our tmp, before it goes out of scope.
            templateBody += "${declName} = tmp;"

        templateBody = wrapObjectTemplate(templateBody, type,
                                          "${declName} = NULL",
                                          failureCode)

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

    if type.isSpiderMonkeyInterface():
        assert not isEnforceRange and not isClamp
        if isMember:
            raise TypeError("Can't handle member arraybuffers or "
                            "arraybuffer views because making sure all the "
                            "objects are properly rooted is hard")
        name = type.name
        # By default, we use a Maybe<> to hold our typed array.  And in the optional
        # non-nullable case we want to pass Optional<TypedArray> to consumers, not
        # Optional<NonNull<TypedArray> >, so jump though some hoops to do that.
        holderType = "Maybe<%s>" % name
        constructLoc = "${holderName}"
        constructMethod = "construct"
        constructInternal = "ref"
        if type.nullable():
            if isOptional:
                declType = "Optional<" + name + "*>"
            else:
                declType = name + "*"
        else:
            if isOptional:
                declType = "Optional<" + name + ">"
                # We don't need a holder in this case
                holderType = None
                constructLoc = "${declName}"
                constructMethod = "Construct"
                constructInternal = "Value"
            else:
                declType = "NonNull<" + name + ">"
        template = (
            "%s.%s(&${val}.toObject());\n"
            "if (!%s.%s().inited()) {\n"
            "%s" # No newline here because onFailureBadType() handles that
            "}\n" %
            (constructLoc, constructMethod, constructLoc, constructInternal,
             CGIndenter(onFailureBadType(failureCode, type.name)).define()))
        nullableTarget = ""
        if type.nullable():
            if isOptional:
                template += "${declName}.Construct();\n"
                nullableTarget = "${declName}.Value()"
            else:
                nullableTarget = "${declName}"
            template += "%s = ${holderName}.addr();" % nullableTarget
        elif not isOptional:
            template += "${declName} = ${holderName}.addr();"
        template = wrapObjectTemplate(template, type,
                                      "%s = NULL" % nullableTarget,
                                      failureCode)

        if holderType is not None:
            holderType = CGGeneric(holderType)
        # We handle all the optional stuff ourselves; no need for caller to do it.
        return (template, CGGeneric(declType), holderType, False)

    if type.isString():
        assert not isEnforceRange and not isClamp

        treatAs = {
            "Default": "eStringify",
            "EmptyString": "eEmpty",
            "Null": "eNull"
        }
        if type.nullable():
            # For nullable strings null becomes a null string.
            treatNullAs = "Null"
            # For nullable strings undefined becomes a null string unless
            # specified otherwise.
            if treatUndefinedAs == "Default":
                treatUndefinedAs = "Null"
        nullBehavior = treatAs[treatNullAs]
        if treatUndefinedAs == "Missing":
            raise TypeError("We don't support [TreatUndefinedAs=Missing]")
        undefinedBehavior = treatAs[treatUndefinedAs]

        def getConversionCode(varName):
            conversionCode = (
                "if (!ConvertJSValueToString(cx, ${val}, ${valPtr}, %s, %s, %s)) {\n"
                "%s\n"
                "}" % (nullBehavior, undefinedBehavior, varName,
                       exceptionCodeIndented.define()))
            if defaultValue is None:
                return conversionCode

            if isinstance(defaultValue, IDLNullValue):
                assert(type.nullable())
                return handleDefault(conversionCode,
                                     "%s.SetNull()" % varName)
            return handleDefault(
                conversionCode,
                ("static const PRUnichar data[] = { %s };\n"
                 "%s.SetData(data, ArrayLength(data) - 1)" %
                 (", ".join(["'" + char + "'" for char in defaultValue.value] + ["0"]),
                  varName)))

        if isMember:
            # We have to make a copy, because our jsval may well not
            # live as long as our string needs to.
            declType = CGGeneric("nsString")
            return (
                "{\n"
                "  FakeDependentString str;\n"
                "%s\n"
                "  ${declName} = str;\n"
                "}\n" % CGIndenter(CGGeneric(getConversionCode("str"))).define(),
                declType, None, isOptional)

        if isOptional:
            declType = "Optional<nsAString>"
        else:
            declType = "NonNull<nsAString>"

        return (
            "%s\n"
            "${declName} = &${holderName};" %
            getConversionCode("${holderName}"),
            CGGeneric(declType), CGGeneric("FakeDependentString"),
            # No need to deal with Optional here; we have handled it already
            False)

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

        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;"
            handleInvalidEnumValueCode = (
                "  if (index < 0) {\n"
                "    return true;\n"
                "  }\n")
            
        template = (
            "{\n"
            "  bool ok;\n"
            "  int index = FindEnumStringIndex<%(invalidEnumValueFatal)s>(cx, ${val}, %(values)s, \"%(enumtype)s\", &ok);\n"
            "  if (!ok) {\n"
            "%(exceptionCode)s\n"
            "  }\n"
            "%(handleInvalidEnumValueCode)s"
            "  %(enumLoc)s = static_cast<%(enumtype)s>(index);\n"
            "}" % { "enumtype" : enumName,
                      "values" : enumName + "Values::strings",
       "invalidEnumValueFatal" : toStringBool(invalidEnumValueFatal),
  "handleInvalidEnumValueCode" : handleInvalidEnumValueCode,
               "exceptionCode" : CGIndenter(exceptionCodeIndented).define(),
                     "enumLoc" : enumLoc,
                    })

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

        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 = %sValues::%s" %
                                          (enumLoc, enumName,
                                           getEnumValueName(defaultValue.value))))
        return (template, CGGeneric(declType), None, isOptional)

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

        if descriptorProvider.workers:
            if isMember:
                raise NoSuchDescriptorError("Can't handle member callbacks in "
                                            "workers; need to sort out rooting"
                                            "issues")
            if type.nullable():
                declType = CGGeneric("JSObject*")
            else:
                declType = CGGeneric("NonNull<JSObject>")
            conversion = "  ${declName} = &${val}.toObject();\n"
        else:
            name = type.unroll().identifier.name
            if type.nullable():
                declType = CGGeneric("nsRefPtr<%s>" % name);
            else:
                declType = CGGeneric("OwningNonNull<%s>" % name)
            conversion = (
                "  ${declName} = new %s(&${val}.toObject());\n" % name)

        if allowTreatNonCallableAsNull and type.treatNonCallableAsNull():
            haveCallable = "JS_ObjectIsCallable(cx, &${val}.toObject())"
            if not isDefinitelyObject:
                haveCallable = "${val}.isObject() && " + haveCallable
            if defaultValue is not None:
                assert(isinstance(defaultValue, IDLNullValue))
                haveCallable = "${haveValue} && " + haveCallable
            template = (
                ("if (%s) {\n" % haveCallable) +
                conversion +
                "} else {\n"
                "  ${declName} = nullptr;\n"
                "}")
        else:
            template = wrapObjectTemplate(
                "if (JS_ObjectIsCallable(cx, &${val}.toObject())) {\n" +
                conversion +
                "} else {\n"
                "%s"
                "}" % CGIndenter(onFailureNotCallable(failureCode)).define(),
                type,
                "${declName} = nullptr",
                failureCode)
        return (template, declType, None, isOptional)

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

        if isMember == "Dictionary" or not isMember:
            declType = "LazyRootedValue"
            templateBody = "${declName}.construct(cx, ${val});"
            nullHandling = "${declName}.construct(cx, JS::NullValue());"
        elif isMember != "Variadic":
            raise TypeError("Can't handle sequence member 'any'; need to sort "
                            "out rooting issues")
        else:
            # Variadic arguments are rooted by being in argv
            declType = "JS::Value"
            templateBody = "${declName} = ${val};"
            nullHandling = "${declName} = JS::NullValue()"

        templateBody = handleDefaultNull(templateBody, nullHandling)
        return (templateBody, CGGeneric(declType), None, isOptional)

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

    if type.isDictionary():
        if failureCode is not None and not isDefinitelyObject:
            raise TypeError("Can't handle dictionaries when failureCode is "
                            "not None and we don't know we're an object")

        # There are no nullable dictionaries
        assert not type.nullable()
        # All optional dictionaries always have default values, so we
        # should be able to assume not isOptional here.
        assert not isOptional

        typeName = CGDictionary.makeDictionaryName(type.inner,
                                                   descriptorProvider.workers)
        actualTypeName = typeName

        declType = CGGeneric(actualTypeName)

        # We do manual default value handling here, because we
        # actually do want a jsval, and we only handle 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, IDLNullValue))
            val = "(${haveValue}) ? ${valHandle} : JS::NullHandleValue"
        else:
            val = "${valHandle}"

        if failureCode is not None:
            assert isDefinitelyObject
            # Check that the value we have can in fact be converted to
            # a dictionary, and return failureCode if not.
            template = CGIfWrapper(
                CGGeneric(failureCode),
                "!IsConvertibleToDictionary(cx, &${valHandle}.toObject())").define() + "\n\n"
        else:
            template = ""

        template += ("if (!${declName}.Init(cx, %s)) {\n"
                     "%s\n"
                     "}" % (val, exceptionCodeIndented.define()))

        return (template, declType, None, False)

    if type.isVoid():
        assert not isOptional
        # This one only happens for return values, and its easy: Just
        # ignore the jsval.
        return ("", None, None, False)

    if type.isDate():
        assert not isEnforceRange and not isClamp

        declType = CGGeneric("Date")
        if type.nullable():
            declType = CGTemplatedType("Nullable", declType)
            dateVal = "${declName}.SetValue()"
        else:
            dateVal = "${declName}"

        if failureCode is None:
            notDate = ("ThrowErrorMessage(cx, MSG_NOT_DATE);\n"
                       "%s" % exceptionCode)
        else:
            notDate = failureCode

        conversion = (
            "if (!JS_ObjectIsDate(cx, &${val}.toObject()) ||\n"
            "    !%s.SetTimeStamp(cx, &${val}.toObject())) {\n"
            "%s\n"
            "}" %
            (dateVal, CGIndenter(CGGeneric(notDate)).define()))

        conversion = wrapObjectTemplate(conversion, type,
                                        "${declName}.SetNull()")
        return (conversion, declType, None, isOptional)

    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"

    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
        template = (
            "if (%s) {\n"
            "  ${declName}.SetNull();\n"
            "} else if (!ValueToPrimitive<%s, %s>(cx, ${val}, &%s)) {\n"
            "%s\n"
            "}" % (nullCondition, typeName, conversionBehavior,
                   writeLoc, exceptionCodeIndented.define()))
    else:
        assert(defaultValue is None or
               not isinstance(defaultValue, IDLNullValue))
        writeLoc = "${declName}"
        readLoc = writeLoc
        template = (
            "if (!ValueToPrimitive<%s, %s>(cx, ${val}, &%s)) {\n"
            "%s\n"
            "}" % (typeName, conversionBehavior, writeLoc,
                   exceptionCodeIndented.define()))
        declType = CGGeneric(typeName)

    if type.isFloat() and not type.isUnrestricted():
        if lenientFloatCode is not None:
            nonFiniteCode = CGIndenter(CGGeneric(lenientFloatCode)).define()
        else:
            nonFiniteCode = ("  ThrowErrorMessage(cx, MSG_NOT_FINITE);\n"
                             "%s" % exceptionCodeIndented.define())
        template += (" else if (!MOZ_DOUBLE_IS_FINITE(%s)) {\n"
                     "  // Note: MOZ_DOUBLE_IS_FINITE will do the right thing\n"
                     "  //       when passed a non-finite float too.\n"
                     "%s\n"
                     "}" % (readLoc, 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()
        if tag in numericSuffixes:
            # Some numeric literals require a suffix to compile without warnings
            defaultStr = numericValue(tag, defaultValue.value)
        else:
            assert(tag == IDLType.Tags.bool)
            defaultStr = toStringBool(defaultValue.value)
        template = CGWrapper(CGIndenter(CGGeneric(template)),
                             pre="if (${haveValue}) {\n",
                             post=("\n"
                                   "} else {\n"
                                   "  %s = %s;\n"
                                   "}" % (writeLoc, defaultStr))).define()

    return (template, declType, None, isOptional)

def instantiateJSToNativeConversionTemplate(templateTuple, replacements,
                                            argcAndIndex=None):
    """
    Take a tuple as returned by getJSToNativeConversionTemplate and a set of
    replacements as required by the strings in such a tuple, and generate code
    to convert into stack C++ types.

    If argcAndIndex is not None it must be a dict that can be used to
    replace ${argc} and ${index}, where ${index} is the index of this
    argument (0-based) and ${argc} is the total number of arguments.
    """
    (templateBody, declType, holderType, dealWithOptional) = templateTuple

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

    result = CGList([], "\n")
    # Make a copy of "replacements" since we may be about to start modifying it
    replacements = dict(replacements)
    originalHolderName = replacements["holderName"]
    if holderType is not None:
        if dealWithOptional:
            replacements["holderName"] = "%s.Value()" % originalHolderName
            holderType = CGTemplatedType("Optional", holderType)
        result.append(
            CGList([holderType, CGGeneric(" "),
                    CGGeneric(originalHolderName),
                    CGGeneric(";")]))

    originalDeclName = replacements["declName"]
    if declType is not None:
        if dealWithOptional:
            replacements["declName"] = "%s.Value()" % originalDeclName
            declType = CGTemplatedType("Optional", declType)
        result.append(
            CGList([declType, CGGeneric(" "),
                    CGGeneric(originalDeclName),
                    CGGeneric(";")]))

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

    if argcAndIndex is not None:
        if dealWithOptional:
            declConstruct = CGIndenter(
                CGGeneric("%s.Construct();" % originalDeclName))
            if holderType is not None:
                holderConstruct = CGIndenter(
                    CGGeneric("%s.Construct();" % originalHolderName))
            else:
                holderConstruct = None
        else:
            declConstruct = None
            holderConstruct = None

        conversion = CGList(
            [CGGeneric(
                    string.Template("if (${index} < ${argc}) {").substitute(
                        argcAndIndex
                        )),
             declConstruct,
             holderConstruct,
             CGIndenter(conversion),
             CGGeneric("}")],
            "\n")

    result.append(conversion)
    # Add an empty CGGeneric to get an extra newline after the argument
    # conversion.
    result.append(CGGeneric(""))
    return result;

def convertConstIDLValueToJSVal(value):
    if isinstance(value, IDLNullValue):
        return "JSVAL_NULL"
    tag = value.type.tag()
    if tag in [IDLType.Tags.int8, IDLType.Tags.uint8, IDLType.Tags.int16,
               IDLType.Tags.uint16, IDLType.Tags.int32]:
        return "INT_TO_JSVAL(%s)" % (value.value)
    if tag == IDLType.Tags.uint32:
        return "UINT_TO_JSVAL(%sU)" % (value.value)
    if tag in [IDLType.Tags.int64, IDLType.Tags.uint64]:
        return "DOUBLE_TO_JSVAL(%s)" % numericValue(tag, value.value)
    if tag == IDLType.Tags.bool:
        return "JSVAL_TRUE" if value.value else "JSVAL_FALSE"
    if tag in [IDLType.Tags.float, IDLType.Tags.double]:
        return "DOUBLE_TO_JSVAL(%s)" % (value.value)
    raise TypeError("Const value of unhandled type: " + value.type)

class CGArgumentConverter(CGThing):
    """
    A class that takes an IDL argument object, its index in the
    argument list, and the argv and argc strings and generates code to
    unwrap the argument to the right native type.
    """
    def __init__(self, argument, index, argv, argc, descriptorProvider,
                 invalidEnumValueFatal=True, lenientFloatCode=None,
                 allowTreatNonCallableAsNull=False):
        CGThing.__init__(self)
        self.argument = argument
        assert(not argument.defaultValue or argument.optional)

        replacer = {
            "index" : index,
            "argc" : argc,
            "argv" : argv
            }
        self.replacementVariables = {
            "declName" : "arg%d" % index,
            "holderName" : ("arg%d" % index) + "_holder",
            "obj" : "obj"
            }
        self.replacementVariables["val"] = string.Template(
            "${argv}[${index}]"
            ).substitute(replacer)
        self.replacementVariables["valPtr"] = (
            "&" + self.replacementVariables["val"])
        self.replacementVariables["valHandle"] = (
            "JS::Handle<JS::Value>::fromMarkedLocation(%s)" %
            self.replacementVariables["valPtr"])
        if argument.defaultValue:
            self.replacementVariables["haveValue"] = string.Template(
                "${index} < ${argc}").substitute(replacer)
        self.descriptorProvider = descriptorProvider
        if self.argument.optional and not self.argument.defaultValue:
            self.argcAndIndex = replacer
        else:
            self.argcAndIndex = None
        self.invalidEnumValueFatal = invalidEnumValueFatal
        self.lenientFloatCode = lenientFloatCode
        self.allowTreatNonCallableAsNull = allowTreatNonCallableAsNull

    def define(self):
        typeConversion = getJSToNativeConversionTemplate(
            self.argument.type,
            self.descriptorProvider,
            isOptional=(self.argcAndIndex is not None and
                        not self.argument.variadic),
            invalidEnumValueFatal=self.invalidEnumValueFatal,
            defaultValue=self.argument.defaultValue,
            treatNullAs=self.argument.treatNullAs,
            treatUndefinedAs=self.argument.treatUndefinedAs,
            isEnforceRange=self.argument.enforceRange,
            isClamp=self.argument.clamp,
            lenientFloatCode=self.lenientFloatCode,
            isMember="Variadic" if self.argument.variadic else False,
            allowTreatNonCallableAsNull=self.allowTreatNonCallableAsNull)

        if not self.argument.variadic:
            return instantiateJSToNativeConversionTemplate(
                typeConversion,
                self.replacementVariables,
                self.argcAndIndex).define()

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

        replacer = dict(self.argcAndIndex, **self.replacementVariables)
        replacer["seqType"] = CGTemplatedType("AutoSequence", elementDeclType).define()
        replacer["elemType"] = elementDeclType.define()

        # NOTE: Keep this in sync with sequence conversions as needed
        variadicConversion = string.Template("""${seqType} ${declName};
if (${argc} > ${index}) {
  if (!${declName}.SetCapacity(${argc} - ${index})) {
    JS_ReportOutOfMemory(cx);
    return false;
  }
  for (uint32_t variadicArg = ${index}; variadicArg < ${argc}; ++variadicArg) {
    ${elemType}& slot = *${declName}.AppendElement();
""").substitute(replacer)

        val = string.Template("${argv}[variadicArg]").substitute(replacer)
        variadicConversion += CGIndenter(CGGeneric(
                string.Template(elementTemplate).substitute(
                    {
                        "val" : val,
                        "valPtr": "&" + val,
                        "valHandle" : ("JS::Handle<JS::Value>::fromMarkedLocation(&%s)" %
                                       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"]
                        }
                    )), 4).define()

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

sequenceWrapLevel = 0

def getWrapTemplateForType(type, descriptorProvider, result, successCode,
                           isCreator, exceptionCode, isMember=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.  The resulting string should be used with string.Template, it
    needs the following keys when substituting: jsvalPtr/jsvalRef/obj.

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

    # We often want exceptionCode to be indented, since it often appears in an
    # if body.
    exceptionCodeIndented = CGIndenter(CGGeneric(exceptionCode))

    def setValue(value, callWrapValue=False):
        """
        Returns the code to set the jsval to value. If "callWrapValue" is true
        MaybeWrapValue will be called on the jsval.
        """
        if not callWrapValue:
            tail = successCode
        else:
            tail = ("if (!MaybeWrapValue(cx, ${jsvalPtr})) {\n" +
                    ("%s\n" % exceptionCodeIndented.define()) +
                    "}\n" +
                    successCode)
        return ("${jsvalRef} = %s;\n" +
                tail) % (value)

    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
        str = ("if (!%s) {\n" +
               CGIndenter(CGGeneric(failureCode)).define() + "\n" +
               "}\n" +
               successCode) % (wrapCall)
        return str

    if type is None or type.isVoid():
        return (setValue("JSVAL_VOID"), True)

    if type.isArray():
        raise TypeError("Can't handle array return values yet")

    if type.isSequence():
        if type.nullable():
            # Nullable sequences are Nullable< nsTArray<T> >
            (recTemplate, recInfall) = getWrapTemplateForType(type.inner, descriptorProvider,
                                                              "%s.Value()" % result, successCode,
                                                              isCreator, exceptionCode)
            return ("""
if (%s.IsNull()) {
%s
}
%s""" % (result, CGIndenter(CGGeneric(setValue("JSVAL_NULL"))).define(), recTemplate), recInfall)

        # 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;",
                'jsvalRef': "tmp",
                'jsvalPtr': "tmp.address()",
                'isCreator': isCreator,
                'exceptionCode': exceptionCode,
                'obj': "returnArray"
                }
            )
        sequenceWrapLevel -= 1
        innerTemplate = CGIndenter(CGGeneric(innerTemplate), 6).define()
        return (("""
uint32_t length = %s.Length();
JS::Rooted<JSObject*> returnArray(cx, JS_NewArrayObject(cx, length, nullptr));
if (!returnArray) {
%s
}
// Scope for 'tmp'
{
  JS::Rooted<JS::Value> tmp(cx);
  for (uint32_t %s = 0; %s < length; ++%s) {
    // Control block to let us common up the JS_DefineElement calls when there
    // are different ways to succeed at wrapping the object.
    do {
%s
    } while (0);
    if (!JS_DefineElement(cx, returnArray, %s, tmp,
                          nullptr, nullptr, JSPROP_ENUMERATE)) {
%s
    }
  }
}\n""" % (result, exceptionCodeIndented.define(),
          index, index, index,
          innerTemplate, index,
          CGIndenter(exceptionCodeIndented, 4).define())) +
                setValue("JS::ObjectValue(*returnArray)"), False)

    if (type.isGeckoInterface() and
        (not type.isCallbackInterface() or
         type.unroll().inner.identifier.name == "EventListener")):
        descriptor = descriptorProvider.getDescriptor(type.unroll().inner.identifier.name)
        if type.nullable():
            wrappingCode = ("if (!%s) {\n" % (result) +
                            CGIndenter(CGGeneric(setValue("JSVAL_NULL"))).define() + "\n" +
                            "}\n")
        else:
            wrappingCode = ""

        if not descriptor.interface.isExternal() and not descriptor.skipGen:
            if descriptor.wrapperCache:
                assert descriptor.nativeOwnership != 'owned'
                wrapMethod = "WrapNewBindingObject"
            else:
                if not isCreator:
                    raise MethodNotCreatorError(descriptor.interface.identifier.name)
                if descriptor.nativeOwnership == 'owned':
                    wrapMethod = "WrapNewBindingNonWrapperCachedOwnedObject"
                else:
                    wrapMethod = "WrapNewBindingNonWrapperCachedObject"
            wrap = "%s(cx, ${obj}, %s, ${jsvalPtr})" % (wrapMethod, result)
            if not descriptor.hasXPConnectImpls:
                # Can only fail to wrap as a new-binding object
                # if they already threw an exception.
                failed = ("MOZ_ASSERT(JS_IsExceptionPending(cx));\n" +
                          "%s" % exceptionCode)
            else:
                if descriptor.notflattened:
                    raise TypeError("%s has XPConnect impls but not flattened; "
                                    "fallback won't work correctly" %
                                    descriptor.interface.identifier.name)
                # Try old-style wrapping for bindings which might be XPConnect impls.
                failed = wrapAndSetPtr("HandleNewBindingWrappingFailure(cx, ${obj}, %s, ${jsvalPtr})" % result)
        else:
            if descriptor.notflattened:
                getIID = "&NS_GET_IID(%s), " % descriptor.nativeType
            else:
                getIID = ""
            wrap = "WrapObject(cx, ${obj}, %s, %s${jsvalPtr})" % (result, getIID)
            failed = None

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

    if type.isString():
        if type.nullable():
            return (wrapAndSetPtr("xpc::StringToJsval(cx, %s, ${jsvalPtr})" % result), False)
        else:
            return (wrapAndSetPtr("xpc::NonVoidStringToJsval(cx, %s, ${jsvalPtr})" % result), False)

    if type.isEnum():
        if type.nullable():
            resultLoc = "%s.Value()" % result
        else:
            resultLoc = result
        conversion = ("""{
  // Scope for resultStr
  MOZ_ASSERT(uint32_t(%(result)s) < ArrayLength(%(strings)s));
  JSString* resultStr = JS_NewStringCopyN(cx, %(strings)s[uint32_t(%(result)s)].value, %(strings)s[uint32_t(%(result)s)].length);
  if (!resultStr) {
%(exceptionCode)s
  }
""" % { "result" : resultLoc,
        "strings" : type.unroll().inner.identifier.name + "Values::strings",
        "exceptionCode" : CGIndenter(exceptionCodeIndented).define() } +
        CGIndenter(CGGeneric(setValue("JS::StringValue(resultStr)"))).define() +
                      "\n}")

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

    if type.isCallback() or type.isCallbackInterface():
        # See comments in WrapNewBindingObject explaining why we need
        # to wrap here.
        # NB: setValue(..., True) calls JS_WrapValue(), so is fallible
        if descriptorProvider.workers:
            return (setValue("JS::ObjectOrNullValue(%s)" % result, True), False)

        wrapCode = setValue(
            "JS::ObjectValue(*GetCallbackFromCallbackObject(%(result)s))",
            True)
        if type.nullable():
            wrapCode = (
                "if (%(result)s) {\n" +
                CGIndenter(CGGeneric(wrapCode)).define() + "\n"
                "} else {\n" +
                CGIndenter(CGGeneric(setValue("JS::NullValue()"))).define() + "\n"
                "}")
        wrapCode = wrapCode % { "result": result }
        return wrapCode, False

    if type.isAny():
        # See comments in WrapNewBindingObject explaining why we need
        # to wrap here.
        # NB: setValue(..., True) calls JS_WrapValue(), so is fallible
        return (setValue(result, True), False)

    if type.isObject() or type.isSpiderMonkeyInterface():
        # See comments in WrapNewBindingObject explaining why we need
        # to wrap here.
        if type.nullable():
            toValue = "JS::ObjectOrNullValue(%s)"
        else:
            if isMember:
                toValue = "JS::ObjectValue(%s)"
            else:
                toValue = "JS::ObjectValue(*%s)"
        # NB: setValue(..., True) calls JS_WrapValue(), so is fallible
        return (setValue(toValue % result, True), False)

    if type.isUnion():
        if type.nullable():
            prefix = "%s->"
        else:
            prefix = "%s."
        return (wrapAndSetPtr((prefix % result) +
                              "ToJSVal(cx, ${obj}, ${jsvalPtr})"), False)

    if not (type.isPrimitive() or type.isDictionary() or type.isDate()):
        raise TypeError("Need to learn to wrap %s" % type)

    if type.nullable():
        (recTemplate, recInfal) = getWrapTemplateForType(type.inner, descriptorProvider,
                                                         "%s.Value()" % result, successCode,
                                                         isCreator, exceptionCode)
        return ("if (%s.IsNull()) {\n" % result +
                CGIndenter(CGGeneric(setValue("JSVAL_NULL"))).define() + "\n" +
                "}\n" + recTemplate, recInfal)

    if type.isDictionary():
        return (wrapAndSetPtr("%s.ToObject(cx, ${obj}, ${jsvalPtr})" % result),
                False)

    if type.isDate():
        return (wrapAndSetPtr("%s.ToDateObject(cx, ${jsvalPtr})" % result),
                False)

    tag = type.tag()

    if tag in [IDLType.Tags.int8, IDLType.Tags.uint8, IDLType.Tags.int16,
               IDLType.Tags.uint16, IDLType.Tags.int32]:
        return (setValue("INT_TO_JSVAL(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 (setValue("JS_NumberValue(double(%s))" % result), True)

    elif tag == IDLType.Tags.uint32:
        return (setValue("UINT_TO_JSVAL(%s)" % result), True)

    elif tag == IDLType.Tags.bool:
        return (setValue("BOOLEAN_TO_JSVAL(%s)" % result), True)

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

def wrapForType(type, descriptorProvider, templateValues, isMember=False):
    """
    Reflect a C++ value of IDL type "type" into JS.  isMember should
    be true if the type is of a dictionary member. TemplateValues is a dict
    that should contain:

      * 'jsvalRef': a C++ reference to the jsval in which to store the result of
                    the conversion
      * 'jsvalPtr': a C++ pointer to the jsval in which to store the result of
                    the conversion
      * '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
      * 'isCreator' (optional): If true, we're wrapping for the return value of
                                a [Creator] 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.
    """
    wrap = getWrapTemplateForType(type, descriptorProvider,
                                  templateValues.get('result', 'result'),
                                  templateValues.get('successCode', None),
                                  templateValues.get('isCreator', False),
                                  templateValues.get('exceptionCode',
                                                     "return false;"),
                                  isMember)[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 isCreator, 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,\
                                  memberIsCreator(member), "return false;")[1]

def typeNeedsCx(type, descriptorProvider, retVal=False):
    if type is None:
        return False
    if type.nullable():
        type = type.inner
    if type.isSequence() or type.isArray():
        type = type.inner
    if type.isUnion():
        return any(typeNeedsCx(t, descriptorProvider) for t in
                   type.unroll().flatMemberTypes)
    if type.isDictionary():
        return dictionaryNeedsCx(type.inner, descriptorProvider)
    if retVal and type.isSpiderMonkeyInterface():
        return True
    if type.isCallback():
        return descriptorProvider.workers
    return type.isAny() or type.isObject()

def dictionaryNeedsCx(dictionary, descriptorProvider):
    return (any(typeNeedsCx(m.type, descriptorProvider) for m in dictionary.members) or
        (dictionary.parent and dictionaryNeedsCx(dictionary.parent, descriptorProvider)))

# Returns a tuple consisting of a CGThing containing the type of the return
# value, or None if there is no need for a return value, and a boolean signaling
# whether the return value is passed in an out parameter.
#
# Whenever this is modified, please update CGNativeMember.getRetvalInfo as
# needed to keep the types compatible.
def getRetvalDeclarationForType(returnType, descriptorProvider,
                                resultAlreadyAddRefed,
                                isMember=False):
    if returnType is None or returnType.isVoid():
        # Nothing to declare
        return None, False
    if returnType.isPrimitive() and returnType.tag() in builtinNames:
        result = CGGeneric(builtinNames[returnType.tag()])
        if returnType.nullable():
            result = CGTemplatedType("Nullable", result)
        return result, False
    if returnType.isString():
        if isMember:
            return CGGeneric("nsString"), True
        return CGGeneric("DOMString"), True
    if returnType.isEnum():
        result = CGGeneric(returnType.unroll().inner.identifier.name)
        if returnType.nullable():
            result = CGTemplatedType("Nullable", result)
        return result, False
    if returnType.isGeckoInterface():
        result = CGGeneric(descriptorProvider.getDescriptor(
            returnType.unroll().inner.identifier.name).nativeType)
        if resultAlreadyAddRefed:
            result = CGTemplatedType("nsRefPtr", result)
        elif descriptorProvider.getDescriptor(
            returnType.unroll().inner.identifier.name).nativeOwnership == 'owned':
            result = CGTemplatedType("nsAutoPtr", result)
        else:
            result = CGWrapper(result, post="*")
        return result, False
    if returnType.isCallback():
        name = returnType.unroll().identifier.name
        if descriptorProvider.workers:
            return CGGeneric("JSObject*"), False
        return CGGeneric("nsRefPtr<%s>" % name), False
    if returnType.isAny():
        return CGGeneric("JS::Value"), False
    if returnType.isObject() or returnType.isSpiderMonkeyInterface():
        return CGGeneric("JSObject*"), False
    if returnType.isSequence():
        nullable = returnType.nullable()
        if nullable:
            returnType = returnType.inner
        # If our result is already addrefed, use the right type in the
        # sequence argument here.
        (result, _) = getRetvalDeclarationForType(returnType.inner,
                                                  descriptorProvider,
                                                  resultAlreadyAddRefed,
                                                  isMember=True)
        result = CGTemplatedType("nsTArray", result)
        if nullable:
            result = CGTemplatedType("Nullable", result)
        return result, True
    if returnType.isDictionary():
        nullable = returnType.nullable()
        result = CGGeneric(
            CGDictionary.makeDictionaryName(returnType.unroll().inner,
                                            descriptorProvider.workers) +
            "Initializer")
        if nullable:
            result = CGTemplatedType("Nullable", result)
        return result, True
    if returnType.isUnion():
        raise TypeError("Need to sort out ownership model for union retvals");
    if returnType.isDate():
        result = CGGeneric("Date")
        if returnType.nullable():
            result = CGTemplatedType("Nullable", result)
        return result, False
    raise TypeError("Don't know how to declare return value for %s" %
                    returnType)

def isResultAlreadyAddRefed(descriptor, extendedAttributes):
    # Default to already_AddRefed on the main thread, raw pointer in workers
    return not descriptor.workers and not 'resultNotAddRefed' in extendedAttributes

def needCx(returnType, arguments, extendedAttributes, descriptorProvider,
           considerTypes):
    return (considerTypes and
            (typeNeedsCx(returnType, descriptorProvider, True) or
             any(typeNeedsCx(a.type, descriptorProvider) for a in arguments)) or
            'implicitJSContext' in extendedAttributes)

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.

    errorReport should be a CGThing for an error report or None if no
    error reporting is needed.
    """
    def __init__(self, errorReport, arguments, argsPre, returnType,
                 extendedAttributes, descriptorProvider, nativeMethodName,
                 static, object="self"):
        CGThing.__init__(self)

        assert errorReport is None or isinstance(errorReport, CGThing)

        isFallible = errorReport is not None

        resultAlreadyAddRefed = isResultAlreadyAddRefed(descriptorProvider,
                                                        extendedAttributes)
        (result, resultOutParam) = getRetvalDeclarationForType(returnType,
                                                               descriptorProvider,
                                                               resultAlreadyAddRefed)

        args = CGList([CGGeneric(arg) for arg in argsPre], ", ")
        for (a, name) in arguments:
            # This is a workaround for a bug in Apple's clang.
            if a.type.isObject() and not a.type.nullable() and not a.optional:
                name = "(JSObject&)" + name
            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.nullable():
                    return True
                if a.type.isString():
                    return True
                if a.optional and not a.defaultValue:
                    # If a.defaultValue, then it's not going to use an Optional,
                    # so doesn't need to be const just due to being optional.
                    # This also covers variadic arguments.
                    return True
                if a.type.isUnion():
                    return True
                return False
            if needsConst(a):
                arg = CGWrapper(arg, pre="Constify(", post=")")
            args.append(arg)

        # Return values that go in outparams go here
        if resultOutParam:
            args.append(CGGeneric("result"))
        if isFallible:
            args.append(CGGeneric("rv"))

        # Build up our actual call
        self.cgRoot = CGList([], "\n")

        call = CGGeneric(nativeMethodName)
        if not static:
            call = CGWrapper(call, pre="%s->" % object)
        call = CGList([call, CGWrapper(args, pre="(", post=");")])
        if result is not None:
            result = CGWrapper(result, post=" result;")
            self.cgRoot.prepend(result)
            if not resultOutParam:
                call = CGWrapper(call, pre="result = ")

        call = CGWrapper(call)
        self.cgRoot.append(call)

        if isFallible:
            self.cgRoot.prepend(CGGeneric("ErrorResult rv;"))
            self.cgRoot.append(CGGeneric("rv.WouldReportJSException();"));
            self.cgRoot.append(CGGeneric("if (rv.Failed()) {"))
            self.cgRoot.append(CGIndenter(errorReport))
            self.cgRoot.append(CGGeneric("}"))

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

class MethodNotCreatorError(Exception):
    def __init__(self, typename):
        self.typename = typename

# 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

def wrapTypeIntoCurrentCompartment(type, value):
    """
    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()
        return CGGeneric("if (!JS_WrapValue(cx, &%s)) {\n"
                         "  return false;\n"
                         "}" % value)

    if type.isObject():
        if not type.nullable():
            value = "%s.Slot()" % value
        else:
            value = "&%s" % value
        return CGGeneric("if (!JS_WrapObject(cx, %s)) {\n"
                         "  return false;\n"
                         "}" % value)

    if type.isSpiderMonkeyInterface():
        raise TypeError("Can't handle wrapping of spidermonkey interfaces in "
                        "constructor arguments yet")

    if type.isSequence():
        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
        return CGWrapper(CGIndenter(wrapElement),
                         pre=("for (uint32_t %s = 0; %s < %s.Length(); ++%s) {\n" %
                              (index, index, value, index)),
                         post="\n}")

    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, "\n") if len(memberWraps) != 0 else None

    if type.isUnion():
        raise TypeError("Can't handle wrapping of unions in constructor "
                        "arguments yet")

    if (type.isString() or type.isPrimitive() or type.isEnum() or
        type.isGeckoInterface() or type.isCallback()):
        # 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):
    """
    As wrapTypeIntoCurrentCompartment but handles things being optional
    """
    origValue = value
    isOptional = arg.optional and not arg.defaultValue
    if isOptional:
        value = value + ".Value()"
    wrap = wrapTypeIntoCurrentCompartment(arg.type, value)
    if wrap and isOptional:
        wrap = CGIfWrapper(wrap, "%s.WasPassed()" % origValue)
    return wrap

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.
    4) Whether or not this method is static.

    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.
    """
    # 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):
        assert idlNode.isMethod() == (not getter and not setter)
        assert idlNode.isAttr() == (getter or setter)

        CGThing.__init__(self)
        self.returnType = returnType
        self.descriptor = descriptor
        self.idlNode = idlNode
        self.extendedAttributes = descriptor.getExtendedAttributes(idlNode,
                                                                   getter=getter,
                                                                   setter=setter)
        self.arguments = arguments
        self.argCount = len(arguments)
        if self.argCount > argConversionStartsAt:
            # Insert our argv in there
            cgThings = [CGGeneric(self.getArgvDecl())]
        else:
            cgThings = []
        lenientFloatCode = None
        if idlNode.getExtendedAttribute('LenientFloat') is not None:
            if setter:
                lenientFloatCode = "return true;"
            elif idlNode.isMethod():
                lenientFloatCode = ("*vp = JSVAL_VOID;\n"
                                    "return true;")

        argsPre = []
        if static:
            nativeMethodName = "%s::%s" % (descriptor.nativeType,
                                           nativeMethodName)
            globalObjectType = "GlobalObject"
            if descriptor.workers:
                globalObjectType = "Worker" + globalObjectType
            cgThings.append(CGGeneric("""%s global(cx, obj);
if (global.Failed()) {
  return false;
}
""" % globalObjectType))
            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.
        needsCx = needCx(returnType, arguments, self.extendedAttributes,
                         descriptor, not descriptor.interface.isJSImplemented())
        if needsCx and not (static and descriptor.workers):
            argsPre.append("cx")

        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("JS_THIS_VALUE(cx, vp)")

        cgThings.extend([CGArgumentConverter(arguments[i], i, self.getArgv(),
                                             self.getArgc(), self.descriptor,
                                             invalidEnumValueFatal=not setter,
                                             allowTreatNonCallableAsNull=setter,
                                             lenientFloatCode=lenientFloatCode) for
                         i in range(argConversionStartsAt, self.argCount)])

        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<JSAutoCompartment> ac;"))
            xraySteps = [
                CGGeneric("obj = js::CheckedUnwrap(obj);\n"
                          "if (!obj) {\n"
                          "  return false;\n"
                          "}\n"
                          "ac.construct(cx, obj);") ]
            xraySteps.extend(
                wrapArgIntoCurrentCompartment(arg, argname)
                for (arg, argname) in self.getArguments())
            cgThings.append(
                CGIfWrapper(CGList(xraySteps, "\n"),
                            "xpc::WrapperFactory::IsXrayWrapper(obj)"))

        cgThings.append(CGCallGenerator(
                    self.getErrorReport() if self.isFallible() else None,
                    self.getArguments(), argsPre, returnType,
                    self.extendedAttributes, descriptor, nativeMethodName,
                    static))
        self.cgRoot = CGList(cgThings, "\n")

    def getArgv(self):
        return "argv" if self.argCount > 0 else ""
    def getArgvDecl(self):
        return "\nJS::Value* argv = JS_ARGV(cx, vp);\n"
    def getArgc(self):
        return "argc"
    def getArguments(self):
        return [(a, "arg" + str(i)) for (i, a) in enumerate(self.arguments)]

    def isFallible(self):
        return not 'infallible' in self.extendedAttributes

    def wrap_return_value(self):
        isCreator = memberIsCreator(self.idlNode)
        if isCreator:
            # We better be returning addrefed things!
            assert(isResultAlreadyAddRefed(self.descriptor,
                                           self.extendedAttributes) or
                   # Creators can return raw pointers to owned objects
                   (self.returnType.isGeckoInterface() and
                    self.descriptor.getDescriptor(self.returnType.unroll().inner.identifier.name).nativeOwnership == 'owned') or
                   # Workers use raw pointers for new-object return
                   # values or something
                   self.descriptor.workers)

        resultTemplateValues = { 'jsvalRef': '*vp', 'jsvalPtr': 'vp',
                                 'isCreator': isCreator}
        try:
            return wrapForType(self.returnType, self.descriptor,
                               resultTemplateValues)
        except MethodNotCreatorError, err:
            assert not isCreator
            raise TypeError("%s being returned from non-creator method or property %s.%s" %
                            (err.typename,
                             self.descriptor.interface.identifier.name,
                             self.idlNode.identifier.name))

    def getErrorReport(self):
        return CGGeneric('return ThrowMethodFailedWithDetails<%s>(cx, rv, "%s", "%s");'
                         % (toStringBool(not self.descriptor.workers),
                            self.descriptor.interface.identifier.name,
                            self.idlNode.identifier.name))

    def define(self):
        return (self.cgRoot.define() + "\n" + 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], "\n")
        self.prepend(CGWrapper(CGGeneric(expression),
                               pre="switch (", post=") {"));
        if default is not None:
            self.append(
                CGIndenter(
                    CGWrapper(
                        CGIndenter(default),
                        pre="default: {\n",
                        post="\n  break;\n}"
                        )
                    )
                )
                        
        self.append(CGGeneric("}"))

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 (defaulting to False) for whether to fall through.
    """
    def __init__(self, expression, body, fallThrough=False):
        CGList.__init__(self, [], "\n")
        self.append(CGWrapper(CGGeneric(expression), pre="case ", post=": {"))
        bodyList = CGList([body], "\n")
        if fallThrough:
            bodyList.append(CGGeneric("/* Fall through */"))
        else:
            bodyList.append(CGGeneric("break;"))
        self.append(CGIndenter(bodyList));
        self.append(CGGeneric("}"))

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 = '"%s.%s"' % (descriptor.interface.identifier.name, method.identifier.name)

        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)
            

        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([ CGIndenter(getPerSignatureCall(signature)) ])
            requiredArgs = requiredArgCount(signature)


            if requiredArgs > 0:
                code = (
                    "if (argc < %d) {\n"
                    "  return ThrowErrorMessage(cx, MSG_MISSING_ARGUMENTS, %s);\n"
                    "}" % (requiredArgs, methodName))
                self.cgRoot.prepend(
                    CGWrapper(CGIndenter(CGGeneric(code)), pre="\n", post="\n"))
            return

        # Need to find the right overload
        maxArgCount = method.maxArgCount
        allowedArgCounts = method.allowedArgCounts

        argCountCases = []
        for argCount in allowedArgCounts:
            possibleSignatures = method.signaturesForArgCount(argCount)
            if len(possibleSignatures) == 1:
                # easy case!
                signature = possibleSignatures[0]

                # (possibly) important optimization: if signature[1] has >
                # argCount arguments and signature[1][argCount] is optional and
                # there is only one signature for argCount+1, then the
                # signature for argCount+1 is just ourselves and we can fall
                # through.
                if (len(signature[1]) > argCount and
                    signature[1][argCount].optional and
                    (argCount+1) in allowedArgCounts and
                    len(method.signaturesForArgCount(argCount+1)) == 1):
                    argCountCases.append(
                        CGCase(str(argCount), None, True))
                else:
                    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:
                #
                #   void(long... foo);
                #   void(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 = [CGGeneric("JS::Value* argv_start = JS_ARGV(cx, vp);")]
            caseBody.extend([ CGArgumentConverter(possibleSignatures[0][1][i],
                                                  i, "argv_start", "argc",
                                                  descriptor) for i in
                              range(0, distinguishingIndex) ])

            # Select the right overload from our set.
            distinguishingArg = "argv_start[%d]" % distinguishingIndex

            def pickFirstSignature(condition, filterLambda):
                sigs = filter(filterLambda, possibleSignatures)
                assert len(sigs) < 2
                if len(sigs) > 0:
                    if condition is None:
                        caseBody.append(
                            getPerSignatureCall(sigs[0], distinguishingIndex))
                    else:
                        caseBody.append(CGGeneric("if (" + condition + ") {"))
                        caseBody.append(CGIndenter(
                                getPerSignatureCall(sigs[0], distinguishingIndex)))
                        caseBody.append(CGGeneric("}"))
                    return True
                return False

            def tryCall(signature, indent, isDefinitelyObject=False,
                        isNullOrUndefined=False):
                assert not isDefinitelyObject or not isNullOrUndefined
                assert isDefinitelyObject or isNullOrUndefined
                if isDefinitelyObject:
                    failureCode = "break;"
                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.
                testCode = instantiateJSToNativeConversionTemplate(
                    getJSToNativeConversionTemplate(type, descriptor,
                                                    failureCode=failureCode,
                                                    isDefinitelyObject=isDefinitelyObject,
                                                    isNullOrUndefined=isNullOrUndefined),
                    {
                        "declName" : "arg%d" % distinguishingIndex,
                        "holderName" : ("arg%d" % distinguishingIndex) + "_holder",
                        "val" : distinguishingArg,
                        "valHandle" : ("JS::Handle<JS::Value>::fromMarkedLocation(&%s)" %
                                       distinguishingArg),
                        "obj" : "obj"
                        })
                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))

            # First 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 is a
            # primitive, string, or enum, 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 all the argument types other than
            # primitive/string/enum end up inside isObject() checks.  So if our
            # nullable is a primitive/string/enum it's safe to not output the
            # extra branch: we'll fall through to conversion for those types,
            # which correctly handles null as needed, because isObject() will be
            # false for null and undefined.
            nullOrUndefSigs = [s for s in possibleSignatures
                               if ((distinguishingType(s).nullable() and not
                                    distinguishingType(s).isString() and not
                                    distinguishingType(s).isEnum() and not
                                   distinguishingType(s).isPrimitive()) or
                                   distinguishingType(s).isDictionary())]
            # Can't have multiple nullable types here
            assert len(nullOrUndefSigs) < 2
            if len(nullOrUndefSigs) > 0:
                caseBody.append(CGGeneric("if (%s.isNullOrUndefined()) {" %
                                          distinguishingArg))
                tryCall(nullOrUndefSigs[0], 2, isNullOrUndefined=True)
                caseBody.append(CGGeneric("}"))

            # 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 Date object being passed to a Date or "object" arg.
            # 3)  A RegExp object being passed to a RegExp or "object" arg.
            # 4)  A callable object being passed to a callback or "object" arg.
            # 5)  Any non-Date and non-RegExp object being passed to a
            #     array or sequence or callback interface dictionary or
            #     "object" arg.
            #
            # We can can coalesce these five cases together, as long as we make
            # sure to check whether our object works as an interface argument
            # before checking whether it works as an arraylike or dictionary or
            # callback function or callback interface.

            # First grab all the overloads that have a non-callback interface
            # (which includes typed arrays and arraybuffers) 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 Date
            objectSigs.extend(s for s in possibleSignatures
                              if distinguishingType(s).isDate())

            # And all the overloads that take callbacks
            objectSigs.extend(s for s in possibleSignatures
                              if distinguishingType(s).isCallback())

            # Now append all the overloads that take an array or sequence or
            # dictionary or callback interface:
            objectSigs.extend(s for s in possibleSignatures
                              if (distinguishingType(s).isArray() or
                                  distinguishingType(s).isSequence() or
                                  distinguishingType(s).isDictionary() or
                                  distinguishingType(s).isCallbackInterface()))

            # 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, typed arrays,
                # sequences, arrays, and Dates 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()) {" %
                                          distinguishingArg))
                for sig in objectSigs:
                    caseBody.append(CGIndenter(CGGeneric("do {")));
                    # Indent by 4, since we need to indent further
                    # than our "do" statement
                    tryCall(sig, 4, isDefinitelyObject=True)
                    caseBody.append(CGIndenter(CGGeneric("} while (0);")))

                caseBody.append(CGGeneric("}"))

            # The remaining cases are mutually exclusive.  The
            # pickFirstSignature calls are what change caseBody
            # Check for strings or enums
            if pickFirstSignature(None,
                                  lambda s: (distinguishingType(s).isString() or
                                             distinguishingType(s).isEnum())):
                pass
            # Check for primitives
            elif pickFirstSignature(None,
                                    lambda s: distinguishingType(s).isPrimitive()):
                pass
            else:
                # Just throw; we have no idea what we're supposed to
                # do with this.
                caseBody.append(CGGeneric(
                  'return ThrowErrorMessage(cx, MSG_INVALID_ARG, "%s", "%s");'
                  % (str(distinguishingIndex), str(argCount))))

            argCountCases.append(CGCase(str(argCount),
                                        CGList(caseBody, "\n")))

        overloadCGThings = []
        overloadCGThings.append(
            CGGeneric("unsigned argcount = std::min(argc, %du);" %
                      maxArgCount))
        overloadCGThings.append(
            CGSwitch("argcount",
                     argCountCases,
                     CGGeneric("return ThrowErrorMessage(cx, MSG_MISSING_ARGUMENTS, %s);\n" % methodName)))
        overloadCGThings.append(
            CGGeneric('MOZ_NOT_REACHED("We have an always-returning default case");\n'
                      'return false;'))
        self.cgRoot = CGWrapper(CGIndenter(CGList(overloadCGThings, "\n")),
                                pre="\n")

    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):
        CGPerSignatureCall.__init__(self, returnType, [], nativeMethodName,
                                    attr.isStatic(), descriptor, attr,
                                    getter=True)

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, interfaceMember, name="arg"):
        self.type = type
        self.optional = False
        self.variadic = False
        self.defaultValue = None
        self.treatNullAs = interfaceMember.treatNullAs
        self.treatUndefinedAs = interfaceMember.treatUndefinedAs
        self.enforceRange = False
        self.clamp = False
        class FakeIdentifier():
            def __init__(self):
                self.name = name
        self.identifier = FakeIdentifier()

class CGSetterCall(CGPerSignatureCall):
    """
    A class to generate a native object setter call for a particular IDL
    setter.
    """
    def __init__(self, argType, nativeMethodName, descriptor, attr):
        CGPerSignatureCall.__init__(self, None, [FakeArgument(argType, attr)],
                                    nativeMethodName, attr.isStatic(),
                                    descriptor, attr, setter=True)
    def wrap_return_value(self):
        # We have no return value
        return "\nreturn true;"
    def getArgc(self):
        return "1"
    def getArgvDecl(self):
        # We just get our stuff from our last arg no matter what
        return ""

class CGAbstractBindingMethod(CGAbstractStaticMethod):
    """
    Common class to generate the JSNatives for all our methods, getters, and
    setters.  This will generate the function declaration and unwrap the
    |this| 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, args, unwrapFailureCode=None,
                 getThisObj="JS_THIS_OBJECT(cx, vp)"):
        CGAbstractStaticMethod.__init__(self, descriptor, name, "JSBool", args)

        if unwrapFailureCode is None:
            self.unwrapFailureCode = 'return ThrowErrorMessage(cx, MSG_DOES_NOT_IMPLEMENT_INTERFACE, "%s");' % self.descriptor.name
        else:
            self.unwrapFailureCode = unwrapFailureCode
        self.getThisObj = getThisObj

    def definition_body(self):
        # Our descriptor might claim that we're not castable, simply because
        # we're someone's consequential interface.  But for this-unwrapping, we
        # know that we're the real deal.  So fake a descriptor here for
        # consumption by CastableObjectUnwrapper.
        getThis = CGGeneric("""JS::RootedObject obj(cx, %s);
if (!obj) {
  return false;
}

%s* self;""" % (self.getThisObj, self.descriptor.nativeType))
        unwrapThis = CGGeneric(
            str(CastableObjectUnwrapper(
                        self.descriptor,
                        "obj", "self", self.unwrapFailureCode)))
        return CGList([ CGIndenter(getThis), CGIndenter(unwrapThis),
                        self.generate_code() ], "\n").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, args):
        CGAbstractStaticMethod.__init__(self, descriptor, name, "JSBool", args)

    def definition_body(self):
        unwrap = CGGeneric("""JS::RootedObject obj(cx, JS_THIS_OBJECT(cx, vp));
if (!obj) {
  return false;
}
""")
        return CGList([ CGIndenter(unwrap),
                        self.generate_code() ], "\n\n").define()

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

def MakeNativeName(name):
    return name[0].upper() + name[1:]

class CGGenericMethod(CGAbstractBindingMethod):
    """
    A class for generating the C++ code for an IDL method..
    """
    def __init__(self, descriptor):
        args = [Argument('JSContext*', 'cx'), Argument('unsigned', 'argc'),
                Argument('JS::Value*', 'vp')]
        CGAbstractBindingMethod.__init__(self, descriptor, 'genericMethod', args)

    def generate_code(self):
        return CGIndenter(CGGeneric(
            "const JSJitInfo *info = FUNCTION_VALUE_TO_JITINFO(JS_CALLEE(cx, vp));\n"
            "MOZ_ASSERT(info->type == JSJitInfo::Method);\n"
            "JSJitMethodOp method = (JSJitMethodOp)info->op;\n"
            "return method(cx, obj, self, argc, vp);"))

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(method.identifier.name)
        args = [Argument('JSContext*', 'cx'), Argument('JSHandleObject', 'obj'),
                Argument('%s*' % descriptor.nativeType, 'self'),
                Argument('unsigned', 'argc'), Argument('JS::Value*', 'vp')]
        CGAbstractStaticMethod.__init__(self, descriptor, name, 'bool', args)

    def definition_body(self):
        nativeName = CGSpecializedMethod.makeNativeName(self.descriptor,
                                                        self.method)
        return CGMethodCall(nativeName, self.method.isStatic(), self.descriptor,
                            self.method).define()

    @staticmethod
    def makeNativeName(descriptor, method):
        name = method.identifier.name
        return MakeNativeName(descriptor.binaryNames.get(name, name))

class CGLegacyCallHook(CGAbstractBindingMethod):
    """
    Call hook for our object
    """
    def __init__(self, descriptor):
        self._legacycaller = descriptor.operations["LegacyCaller"]
        args = [Argument('JSContext*', 'cx'), Argument('unsigned', 'argc'),
                Argument('JS::Value*', 'vp')]
        # Our "self" is actually the callee in this case, not the thisval.
        CGAbstractBindingMethod.__init__(
            self, descriptor, LEGACYCALLER_HOOK_NAME,
            args, getThisObj="&JS_CALLEE(cx, vp).toObject()")

    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.binaryNames.get(name, name))
        return CGMethodCall(nativeName, False, self.descriptor,
                            self._legacycaller)

class CGNewResolveHook(CGAbstractBindingMethod):
    """
    NewResolve hook for our object
    """
    def __init__(self, descriptor):
        self._needNewResolve = descriptor.interface.getExtendedAttribute("NeedNewResolve")
        args = [Argument('JSContext*', 'cx'), Argument('JSHandleObject', 'obj_'),
                Argument('JSHandleId', 'id'), Argument('unsigned', 'flags'),
                Argument('JS::MutableHandle<JSObject*>', 'objp')]
        # Our "self" is actually the callee in this case, not the thisval.
        CGAbstractBindingMethod.__init__(
            self, descriptor, NEWRESOLVE_HOOK_NAME,
            args, getThisObj="obj_")

    def define(self):
        if not self._needNewResolve:
            return ""
        return CGAbstractBindingMethod.define(self)

    def generate_code(self):
        return CGIndenter(CGGeneric("return self->DoNewResolve(cx, obj, id, flags, objp);"))

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', '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):
        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 = method.identifier.name
        args = [Argument('JSContext*', 'cx'), Argument('unsigned', 'argc'),
                Argument('JS::Value*', 'vp')]
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name, args)

    def generate_code(self):
        nativeName = CGSpecializedMethod.makeNativeName(self.descriptor,
                                                        self.method)
        return CGMethodCall(nativeName, True, self.descriptor, self.method)

class CGGenericGetter(CGAbstractBindingMethod):
    """
    A class for generating the C++ code for an IDL attribute getter.
    """
    def __init__(self, descriptor, lenientThis=False):
        args = [Argument('JSContext*', 'cx'), Argument('unsigned', 'argc'),
                Argument('JS::Value*', 'vp')]
        if lenientThis:
            name = "genericLenientGetter"
            unwrapFailureCode = (
                "MOZ_ASSERT(!JS_IsExceptionPending(cx));\n"
                "ReportLenientThisUnwrappingFailure(cx, obj);\n"
                "JS_SET_RVAL(cx, vp, JS::UndefinedValue());\n"
                "return true;")
        else:
            name = "genericGetter"
            unwrapFailureCode = None
        CGAbstractBindingMethod.__init__(self, descriptor, name, args,
                                         unwrapFailureCode)

    def generate_code(self):
        return CGIndenter(CGGeneric(
            "const JSJitInfo *info = FUNCTION_VALUE_TO_JITINFO(JS_CALLEE(cx, vp));\n"
            "MOZ_ASSERT(info->type == JSJitInfo::Getter);\n"
            "JSJitPropertyOp getter = info->op;\n"
            "return getter(cx, obj, self, vp);"))

class CGSpecializedGetter(CGAbstractStaticMethod):
    """
    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_' + attr.identifier.name
        args = [ Argument('JSContext*', 'cx'),
                 Argument('JSHandleObject', 'obj'),
                 Argument('%s*' % descriptor.nativeType, 'self'),
                 Argument('JS::Value*', 'vp') ]
        CGAbstractStaticMethod.__init__(self, descriptor, name, "bool", args)

    def definition_body(self):
        nativeName = CGSpecializedGetter.makeNativeName(self.descriptor,
                                                        self.attr)
        return CGIndenter(CGGetterCall(self.attr.type, nativeName,
                                       self.descriptor, self.attr)).define()

    @staticmethod
    def makeNativeName(descriptor, attr):
        name = attr.identifier.name
        nativeName = MakeNativeName(descriptor.binaryNames.get(name, name))
        # resultOutParam does not depend on whether resultAlreadyAddRefed is set
        (_, resultOutParam) = getRetvalDeclarationForType(attr.type, descriptor,
                                                          False)
        infallible = ('infallible' in
                      descriptor.getExtendedAttributes(attr, getter=True))
        if resultOutParam or attr.type.nullable() or not infallible:
            nativeName = "Get" + nativeName
        return nativeName

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_' + attr.identifier.name
        args = [Argument('JSContext*', 'cx'), Argument('unsigned', 'argc'),
                Argument('JS::Value*', 'vp')]
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name, args)

    def generate_code(self):
        nativeName = CGSpecializedGetter.makeNativeName(self.descriptor,
                                                        self.attr)
        return CGIndenter(CGGetterCall(self.attr.type, nativeName,
                                       self.descriptor, self.attr))

class CGGenericSetter(CGAbstractBindingMethod):
    """
    A class for generating the C++ code for an IDL attribute setter.
    """
    def __init__(self, descriptor, lenientThis=False):
        args = [Argument('JSContext*', 'cx'), Argument('unsigned', 'argc'),
                Argument('JS::Value*', 'vp')]
        if lenientThis:
            name = "genericLenientSetter"
            unwrapFailureCode = (
                "MOZ_ASSERT(!JS_IsExceptionPending(cx));\n"
                "ReportLenientThisUnwrappingFailure(cx, obj);\n"
                "return true;")
        else:
            name = "genericSetter"
            unwrapFailureCode = None
        CGAbstractBindingMethod.__init__(self, descriptor, name, args,
                                         unwrapFailureCode)

    def generate_code(self):
        return CGIndenter(CGGeneric(
                "if (argc == 0) {\n"
                '  return ThrowErrorMessage(cx, MSG_MISSING_ARGUMENTS, "%s attribute setter");\n'
                "}\n"
                "JS::Value* argv = JS_ARGV(cx, vp);\n"
                "const JSJitInfo *info = FUNCTION_VALUE_TO_JITINFO(JS_CALLEE(cx, vp));\n"
                "MOZ_ASSERT(info->type == JSJitInfo::Setter);\n"
                "JSJitPropertyOp setter = info->op;\n"
                "if (!setter(cx, obj, self, argv)) {\n"
                "  return false;\n"
                "}\n"
                "*vp = JSVAL_VOID;\n"
                "return true;" % self.descriptor.interface.identifier.name))

class CGSpecializedSetter(CGAbstractStaticMethod):
    """
    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_' + attr.identifier.name
        args = [ Argument('JSContext*', 'cx'),
                 Argument('JSHandleObject', 'obj'),
                 Argument('%s*' % descriptor.nativeType, 'self'),
                 Argument('JS::Value*', 'argv')]
        CGAbstractStaticMethod.__init__(self, descriptor, name, "bool", args)

    def definition_body(self):
        nativeName = CGSpecializedSetter.makeNativeName(self.descriptor,
                                                        self.attr)
        return CGIndenter(CGSetterCall(self.attr.type, nativeName,
                                       self.descriptor, self.attr)).define()

    @staticmethod
    def makeNativeName(descriptor, attr):
        name = attr.identifier.name
        return "Set" + MakeNativeName(descriptor.binaryNames.get(name, name))

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_' + attr.identifier.name
        args = [Argument('JSContext*', 'cx'), Argument('unsigned', 'argc'),
                Argument('JS::Value*', 'vp')]
        CGAbstractStaticBindingMethod.__init__(self, descriptor, name, args)

    def generate_code(self):
        nativeName = CGSpecializedSetter.makeNativeName(self.descriptor,
                                                        self.attr)
        argv = CGGeneric("""JS::Value* argv = JS_ARGV(cx, vp);
JS::Value undef = JS::UndefinedValue();
if (argc == 0) {
  argv = &undef;
}""")
        call = CGSetterCall(self.attr.type, nativeName, self.descriptor,
                            self.attr)
        return CGIndenter(CGList([ argv, call ], "\n"))

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 CGIndenter(CGGeneric("""JS::RootedValue v(cx);
if (!JS_GetProperty(cx, obj, "%s", v.address())) {
  return false;
}

if (!v.isObject()) {
  return ThrowErrorMessage(cx, MSG_NOT_OBJECT);
}

return JS_SetProperty(cx, &v.toObject(), "%s", argv);""" % (attrName, forwardToAttrName))).define()

def memberIsCreator(member):
    return member.getExtendedAttribute("Creator") 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, constant,
                      pure, returnTypes):
        assert(not constant or pure) # constants are always pure
        protoID = "prototypes::id::%s" % self.descriptor.name
        depth = "PrototypeTraits<%s>::Depth" % protoID
        failstr = toStringBool(infallible)
        conststr = toStringBool(constant)
        purestr = toStringBool(pure)
        returnType = reduce(CGMemberJITInfo.getSingleReturnType, returnTypes,
                            "")
        return ("\n"
                "static const JSJitInfo %s = {\n"
                "  %s,\n"
                "  %s,\n"
                "  %s,\n"
                "  JSJitInfo::%s,\n"
                "  %s,  /* isInfallible. False in setters. */\n"
                "  %s,  /* isConstant. Only relevant for getters. */\n"
                "  %s,  /* isPure.  Only relevant for getters. */\n"
                "  %s   /* returnType.  Only relevant for getters/methods. */\n"
                "};\n" % (infoName, opName, protoID, depth, opType, failstr,
                          conststr, purestr, returnType))

    def define(self):
        if self.member.isAttr():
            getterinfo = ("%s_getterinfo" % self.member.identifier.name)
            getter = ("(JSJitPropertyOp)get_%s" % self.member.identifier.name)
            getterinfal = "infallible" in self.descriptor.getExtendedAttributes(self.member, getter=True)
            getterconst = self.member.getExtendedAttribute("Constant")
            getterpure = getterconst or self.member.getExtendedAttribute("Pure")
            assert (getterinfal or (not getterconst and not getterpure))

            getterinfal = getterinfal and infallibleForMember(self.member, self.member.type, self.descriptor)
            result = self.defineJitInfo(getterinfo, getter, "Getter",
                                        getterinfal, getterconst, getterpure,
                                        [self.member.type])
            if not self.member.readonly or self.member.getExtendedAttribute("PutForwards") is not None:
                setterinfo = ("%s_setterinfo" % self.member.identifier.name)
                setter = ("(JSJitPropertyOp)set_%s" % 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,
                                             [BuiltinTypes[IDLBuiltinType.Types.void]])
            return result
        if self.member.isMethod():
            methodinfo = ("%s_methodinfo" % self.member.identifier.name)
            name = CppKeywords.checkMethodName(self.member.identifier.name)
            # Actually a JSJitMethodOp, but JSJitPropertyOp by struct definition.
            method = ("(JSJitPropertyOp)%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
            else:
                sig = sigs[0]
                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 = "infallible" in self.descriptor.getExtendedAttributes(self.member)

            result = self.defineJitInfo(methodinfo, method, "Method",
                                        methodInfal, False, False,
                                        [s[0] for s in sigs])
            return result
        raise TypeError("Illegal member type to CGPropertyJITInfo")

    @staticmethod
    def getJSReturnTypeTag(t):
        if t.nullable():
            # Sometimes it might return null, sometimes not
            return "JSVAL_TYPE_UNKNOWN"
        if t.isVoid():
            # No return, every time
            return "JSVAL_TYPE_UNDEFINED"
        if t.isArray():
            # No idea yet
            assert False
        if t.isSequence():
            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.