Add m-esr52 at 52.6.0

1 files changed, 6874 insertions, 0 deletions

diff --git a/dom/bindings/parser/WebIDL.py b/dom/bindings/parser/WebIDL.py
new file mode 100644
index 000000000..f668d7d62
--- /dev/null
+++ b/dom/bindings/parser/WebIDL.py
@@ -0,0 +1,6874 @@
+# 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/.
+
+""" A WebIDL parser. """
+
+from ply import lex, yacc
+import re
+import os
+import traceback
+import math
+import string
+from collections import defaultdict
+
+# Machinery
+
+
+def parseInt(literal):
+    string = literal
+    sign = 0
+    base = 0
+
+    if string[0] == '-':
+        sign = -1
+        string = string[1:]
+    else:
+        sign = 1
+
+    if string[0] == '0' and len(string) > 1:
+        if string[1] == 'x' or string[1] == 'X':
+            base = 16
+            string = string[2:]
+        else:
+            base = 8
+            string = string[1:]
+    else:
+        base = 10
+
+    value = int(string, base)
+    return value * sign
+
+
+# Magic for creating enums
+def M_add_class_attribs(attribs, start):
+    def foo(name, bases, dict_):
+        for v, k in enumerate(attribs):
+            dict_[k] = start + v
+        assert 'length' not in dict_
+        dict_['length'] = start + len(attribs)
+        return type(name, bases, dict_)
+    return foo
+
+
+def enum(*names, **kw):
+    if len(kw) == 1:
+        base = kw['base'].__class__
+        start = base.length
+    else:
+        assert len(kw) == 0
+        base = object
+        start = 0
+
+    class Foo(base):
+        __metaclass__ = M_add_class_attribs(names, start)
+
+        def __setattr__(self, name, value):  # this makes it read-only
+            raise NotImplementedError
+    return Foo()
+
+
+class WebIDLError(Exception):
+    def __init__(self, message, locations, warning=False):
+        self.message = message
+        self.locations = [str(loc) for loc in locations]
+        self.warning = warning
+
+    def __str__(self):
+        return "%s: %s%s%s" % (self.warning and 'warning' or 'error',
+                               self.message,
+                               ", " if len(self.locations) != 0 else "",
+                               "\n".join(self.locations))
+
+
+class Location(object):
+    def __init__(self, lexer, lineno, lexpos, filename):
+        self._line = None
+        self._lineno = lineno
+        self._lexpos = lexpos
+        self._lexdata = lexer.lexdata
+        self._file = filename if filename else "<unknown>"
+
+    def __eq__(self, other):
+        return (self._lexpos == other._lexpos and
+                self._file == other._file)
+
+    def filename(self):
+        return self._file
+
+    def resolve(self):
+        if self._line:
+            return
+
+        startofline = self._lexdata.rfind('\n', 0, self._lexpos) + 1
+        endofline = self._lexdata.find('\n', self._lexpos, self._lexpos + 80)
+        if endofline != -1:
+            self._line = self._lexdata[startofline:endofline]
+        else:
+            self._line = self._lexdata[startofline:]
+        self._colno = self._lexpos - startofline
+
+        # Our line number seems to point to the start of self._lexdata
+        self._lineno += self._lexdata.count('\n', 0, startofline)
+
+    def get(self):
+        self.resolve()
+        return "%s line %s:%s" % (self._file, self._lineno, self._colno)
+
+    def _pointerline(self):
+        return " " * self._colno + "^"
+
+    def __str__(self):
+        self.resolve()
+        return "%s line %s:%s\n%s\n%s" % (self._file, self._lineno, self._colno,
+                                          self._line, self._pointerline())
+
+
+class BuiltinLocation(object):
+    def __init__(self, text):
+        self.msg = text + "\n"
+
+    def __eq__(self, other):
+        return (isinstance(other, BuiltinLocation) and
+                self.msg == other.msg)
+
+    def filename(self):
+        return '<builtin>'
+
+    def resolve(self):
+        pass
+
+    def get(self):
+        return self.msg
+
+    def __str__(self):
+        return self.get()
+
+
+# Data Model
+
+
+class IDLObject(object):
+    def __init__(self, location):
+        self.location = location
+        self.userData = dict()
+
+    def filename(self):
+        return self.location.filename()
+
+    def isInterface(self):
+        return False
+
+    def isNamespace(self):
+        return False
+
+    def isEnum(self):
+        return False
+
+    def isCallback(self):
+        return False
+
+    def isType(self):
+        return False
+
+    def isDictionary(self):
+        return False
+
+    def isUnion(self):
+        return False
+
+    def isTypedef(self):
+        return False
+
+    def getUserData(self, key, default):
+        return self.userData.get(key, default)
+
+    def setUserData(self, key, value):
+        self.userData[key] = value
+
+    def addExtendedAttributes(self, attrs):
+        assert False  # Override me!
+
+    def handleExtendedAttribute(self, attr):
+        assert False  # Override me!
+
+    def _getDependentObjects(self):
+        assert False  # Override me!
+
+    def getDeps(self, visited=None):
+        """ Return a set of files that this object depends on.  If any of
+            these files are changed the parser needs to be rerun to regenerate
+            a new IDLObject.
+
+            The visited argument is a set of all the objects already visited.
+            We must test to see if we are in it, and if so, do nothing.  This
+            prevents infinite recursion."""
+
+        # NB: We can't use visited=set() above because the default value is
+        # evaluated when the def statement is evaluated, not when the function
+        # is executed, so there would be one set for all invocations.
+        if visited is None:
+            visited = set()
+
+        if self in visited:
+            return set()
+
+        visited.add(self)
+
+        deps = set()
+        if self.filename() != "<builtin>":
+            deps.add(self.filename())
+
+        for d in self._getDependentObjects():
+            deps.update(d.getDeps(visited))
+
+        return deps
+
+
+class IDLScope(IDLObject):
+    def __init__(self, location, parentScope, identifier):
+        IDLObject.__init__(self, location)
+
+        self.parentScope = parentScope
+        if identifier:
+            assert isinstance(identifier, IDLIdentifier)
+            self._name = identifier
+        else:
+            self._name = None
+
+        self._dict = {}
+        self.globalNames = set()
+        # A mapping from global name to the set of global interfaces
+        # that have that global name.
+        self.globalNameMapping = defaultdict(set)
+        self.primaryGlobalAttr = None
+        self.primaryGlobalName = None
+
+    def __str__(self):
+        return self.QName()
+
+    def QName(self):
+        if self._name:
+            return self._name.QName() + "::"
+        return "::"
+
+    def ensureUnique(self, identifier, object):
+        """
+            Ensure that there is at most one 'identifier' in scope ('self').
+            Note that object can be None.  This occurs if we end up here for an
+            interface type we haven't seen yet.
+        """
+        assert isinstance(identifier, IDLUnresolvedIdentifier)
+        assert not object or isinstance(object, IDLObjectWithIdentifier)
+        assert not object or object.identifier == identifier
+
+        if identifier.name in self._dict:
+            if not object:
+                return
+
+            # ensureUnique twice with the same object is not allowed
+            assert id(object) != id(self._dict[identifier.name])
+
+            replacement = self.resolveIdentifierConflict(self, identifier,
+                                                         self._dict[identifier.name],
+                                                         object)
+            self._dict[identifier.name] = replacement
+            return
+
+        assert object
+
+        self._dict[identifier.name] = object
+
+    def resolveIdentifierConflict(self, scope, identifier, originalObject, newObject):
+        if (isinstance(originalObject, IDLExternalInterface) and
+            isinstance(newObject, IDLExternalInterface) and
+            originalObject.identifier.name == newObject.identifier.name):
+            return originalObject
+
+        if (isinstance(originalObject, IDLExternalInterface) or
+            isinstance(newObject, IDLExternalInterface)):
+            raise WebIDLError(
+                "Name collision between "
+                "interface declarations for identifier '%s' at '%s' and '%s'"
+                % (identifier.name,
+                    originalObject.location, newObject.location), [])
+
+        if (isinstance(originalObject, IDLDictionary) or
+            isinstance(newObject, IDLDictionary)):
+            raise WebIDLError(
+                "Name collision between dictionary declarations for "
+                "identifier '%s'.\n%s\n%s"
+                % (identifier.name,
+                   originalObject.location, newObject.location), [])
+
+        # We do the merging of overloads here as opposed to in IDLInterface
+        # because we need to merge overloads of NamedConstructors and we need to
+        # detect conflicts in those across interfaces. See also the comment in
+        # IDLInterface.addExtendedAttributes for "NamedConstructor".
+        if (isinstance(originalObject, IDLMethod) and
+            isinstance(newObject, IDLMethod)):
+            return originalObject.addOverload(newObject)
+
+        # Default to throwing, derived classes can override.
+        conflictdesc = "\n\t%s at %s\n\t%s at %s" % (originalObject,
+                                                     originalObject.location,
+                                                     newObject,
+                                                     newObject.location)
+
+        raise WebIDLError(
+            "Multiple unresolvable definitions of identifier '%s' in scope '%s%s"
+            % (identifier.name, str(self), conflictdesc), [])
+
+    def _lookupIdentifier(self, identifier):
+        return self._dict[identifier.name]
+
+    def lookupIdentifier(self, identifier):
+        assert isinstance(identifier, IDLIdentifier)
+        assert identifier.scope == self
+        return self._lookupIdentifier(identifier)
+
+
+class IDLIdentifier(IDLObject):
+    def __init__(self, location, scope, name):
+        IDLObject.__init__(self, location)
+
+        self.name = name
+        assert isinstance(scope, IDLScope)
+        self.scope = scope
+
+    def __str__(self):
+        return self.QName()
+
+    def QName(self):
+        return self.scope.QName() + self.name
+
+    def __hash__(self):
+        return self.QName().__hash__()
+
+    def __eq__(self, other):
+        return self.QName() == other.QName()
+
+    def object(self):
+        return self.scope.lookupIdentifier(self)
+
+
+class IDLUnresolvedIdentifier(IDLObject):
+    def __init__(self, location, name, allowDoubleUnderscore=False,
+                 allowForbidden=False):
+        IDLObject.__init__(self, location)
+
+        assert len(name) > 0
+
+        if name == "__noSuchMethod__":
+            raise WebIDLError("__noSuchMethod__ is deprecated", [location])
+
+        if name[:2] == "__" and name != "__content" and not allowDoubleUnderscore:
+            raise WebIDLError("Identifiers beginning with __ are reserved",
+                              [location])
+        if name[0] == '_' and not allowDoubleUnderscore:
+            name = name[1:]
+        # TODO: Bug 872377, Restore "toJSON" to below list.
+        # We sometimes need custom serialization, so allow toJSON for now.
+        if (name in ["constructor", "toString"] and
+            not allowForbidden):
+            raise WebIDLError("Cannot use reserved identifier '%s'" % (name),
+                              [location])
+
+        self.name = name
+
+    def __str__(self):
+        return self.QName()
+
+    def QName(self):
+        return "<unresolved scope>::" + self.name
+
+    def resolve(self, scope, object):
+        assert isinstance(scope, IDLScope)
+        assert not object or isinstance(object, IDLObjectWithIdentifier)
+        assert not object or object.identifier == self
+
+        scope.ensureUnique(self, object)
+
+        identifier = IDLIdentifier(self.location, scope, self.name)
+        if object:
+            object.identifier = identifier
+        return identifier
+
+    def finish(self):
+        assert False  # Should replace with a resolved identifier first.
+
+
+class IDLObjectWithIdentifier(IDLObject):
+    def __init__(self, location, parentScope, identifier):
+        IDLObject.__init__(self, location)
+
+        assert isinstance(identifier, IDLUnresolvedIdentifier)
+
+        self.identifier = identifier
+
+        if parentScope:
+            self.resolve(parentScope)
+
+        self.treatNullAs = "Default"
+
+    def resolve(self, parentScope):
+        assert isinstance(parentScope, IDLScope)
+        assert isinstance(self.identifier, IDLUnresolvedIdentifier)
+        self.identifier.resolve(parentScope, self)
+
+    def checkForStringHandlingExtendedAttributes(self, attrs,
+                                                 isDictionaryMember=False,
+                                                 isOptional=False):
+        """
+        A helper function to deal with TreatNullAs.  Returns the list
+        of attrs it didn't handle itself.
+        """
+        assert isinstance(self, IDLArgument) or isinstance(self, IDLAttribute)
+        unhandledAttrs = list()
+        for attr in attrs:
+            if not attr.hasValue():
+                unhandledAttrs.append(attr)
+                continue
+
+            identifier = attr.identifier()
+            value = attr.value()
+            if identifier == "TreatNullAs":
+                if not self.type.isDOMString() or self.type.nullable():
+                    raise WebIDLError("[TreatNullAs] is only allowed on "
+                                      "arguments or attributes whose type is "
+                                      "DOMString",
+                                      [self.location])
+                if isDictionaryMember:
+                    raise WebIDLError("[TreatNullAs] is not allowed for "
+                                      "dictionary members", [self.location])
+                if value != 'EmptyString':
+                    raise WebIDLError("[TreatNullAs] must take the identifier "
+                                      "'EmptyString', not '%s'" % value,
+                                      [self.location])
+                self.treatNullAs = value
+            else:
+                unhandledAttrs.append(attr)
+
+        return unhandledAttrs
+
+
+class IDLObjectWithScope(IDLObjectWithIdentifier, IDLScope):
+    def __init__(self, location, parentScope, identifier):
+        assert isinstance(identifier, IDLUnresolvedIdentifier)
+
+        IDLObjectWithIdentifier.__init__(self, location, parentScope, identifier)
+        IDLScope.__init__(self, location, parentScope, self.identifier)
+
+
+class IDLIdentifierPlaceholder(IDLObjectWithIdentifier):
+    def __init__(self, location, identifier):
+        assert isinstance(identifier, IDLUnresolvedIdentifier)
+        IDLObjectWithIdentifier.__init__(self, location, None, identifier)
+
+    def finish(self, scope):
+        try:
+            scope._lookupIdentifier(self.identifier)
+        except:
+            raise WebIDLError("Unresolved type '%s'." % self.identifier,
+                              [self.location])
+
+        obj = self.identifier.resolve(scope, None)
+        return scope.lookupIdentifier(obj)
+
+
+class IDLExposureMixins():
+    def __init__(self, location):
+        # _exposureGlobalNames are the global names listed in our [Exposed]
+        # extended attribute.  exposureSet is the exposure set as defined in the
+        # Web IDL spec: it contains interface names.
+        self._exposureGlobalNames = set()
+        self.exposureSet = set()
+        self._location = location
+        self._globalScope = None
+
+    def finish(self, scope):
+        assert scope.parentScope is None
+        self._globalScope = scope
+
+        # Verify that our [Exposed] value, if any, makes sense.
+        for globalName in self._exposureGlobalNames:
+            if globalName not in scope.globalNames:
+                raise WebIDLError("Unknown [Exposed] value %s" % globalName,
+                                  [self._location])
+
+        if len(self._exposureGlobalNames) == 0:
+            self._exposureGlobalNames.add(scope.primaryGlobalName)
+
+        globalNameSetToExposureSet(scope, self._exposureGlobalNames,
+                                   self.exposureSet)
+
+    def isExposedInWindow(self):
+        return 'Window' in self.exposureSet
+
+    def isExposedOnMainThread(self):
+        return (self.isExposedInWindow() or
+                self.isExposedInSystemGlobals())
+
+    def isExposedInAnyWorker(self):
+        return len(self.getWorkerExposureSet()) > 0
+
+    def isExposedInWorkerDebugger(self):
+        return len(self.getWorkerDebuggerExposureSet()) > 0
+
+    def isExposedInAnyWorklet(self):
+        return len(self.getWorkletExposureSet()) > 0
+
+    def isExposedInSystemGlobals(self):
+        return 'BackstagePass' in self.exposureSet
+
+    def isExposedInSomeButNotAllWorkers(self):
+        """
+        Returns true if the Exposed extended attribute for this interface
+        exposes it in some worker globals but not others.  The return value does
+        not depend on whether the interface is exposed in Window or System
+        globals.
+        """
+        if not self.isExposedInAnyWorker():
+            return False
+        workerScopes = self.parentScope.globalNameMapping["Worker"]
+        return len(workerScopes.difference(self.exposureSet)) > 0
+
+    def getWorkerExposureSet(self):
+        workerScopes = self._globalScope.globalNameMapping["Worker"]
+        return workerScopes.intersection(self.exposureSet)
+
+    def getWorkletExposureSet(self):
+        workletScopes = self._globalScope.globalNameMapping["Worklet"]
+        return workletScopes.intersection(self.exposureSet)
+
+    def getWorkerDebuggerExposureSet(self):
+        workerDebuggerScopes = self._globalScope.globalNameMapping["WorkerDebugger"]
+        return workerDebuggerScopes.intersection(self.exposureSet)
+
+
+class IDLExternalInterface(IDLObjectWithIdentifier, IDLExposureMixins):
+    def __init__(self, location, parentScope, identifier):
+        assert isinstance(identifier, IDLUnresolvedIdentifier)
+        assert isinstance(parentScope, IDLScope)
+        self.parent = None
+        IDLObjectWithIdentifier.__init__(self, location, parentScope, identifier)
+        IDLExposureMixins.__init__(self, location)
+        IDLObjectWithIdentifier.resolve(self, parentScope)
+
+    def finish(self, scope):
+        IDLExposureMixins.finish(self, scope)
+        pass
+
+    def validate(self):
+        pass
+
+    def isIteratorInterface(self):
+        return False
+
+    def isExternal(self):
+        return True
+
+    def isInterface(self):
+        return True
+
+    def isConsequential(self):
+        return False
+
+    def addExtendedAttributes(self, attrs):
+        assert len(attrs) == 0
+
+    def resolve(self, parentScope):
+        pass
+
+    def getJSImplementation(self):
+        return None
+
+    def isJSImplemented(self):
+        return False
+
+    def isProbablyShortLivingObject(self):
+        return False
+
+    def isNavigatorProperty(self):
+        return False
+
+    def _getDependentObjects(self):
+        return set()
+
+
+class IDLPartialInterfaceOrNamespace(IDLObject):
+    def __init__(self, location, name, members, nonPartialInterfaceOrNamespace):
+        assert isinstance(name, IDLUnresolvedIdentifier)
+
+        IDLObject.__init__(self, location)
+        self.identifier = name
+        self.members = members
+        # propagatedExtendedAttrs are the ones that should get
+        # propagated to our non-partial interface.
+        self.propagatedExtendedAttrs = []
+        self._haveSecureContextExtendedAttribute = False
+        self._nonPartialInterfaceOrNamespace = nonPartialInterfaceOrNamespace
+        self._finished = False
+        nonPartialInterfaceOrNamespace.addPartialInterface(self)
+
+    def addExtendedAttributes(self, attrs):
+        for attr in attrs:
+            identifier = attr.identifier()
+
+            if identifier in ["Constructor", "NamedConstructor"]:
+                self.propagatedExtendedAttrs.append(attr)
+            elif identifier == "SecureContext":
+                self._haveSecureContextExtendedAttribute = True
+                # This gets propagated to all our members.
+                for member in self.members:
+                    if member.getExtendedAttribute("SecureContext"):
+                        raise WebIDLError("[SecureContext] specified on both a "
+                                          "partial interface member and on the "
+                                          "partial interface itself",
+                                          [member.location, attr.location])
+                    member.addExtendedAttributes([attr])
+            elif identifier == "Exposed":
+                # This just gets propagated to all our members.
+                for member in self.members:
+                    if len(member._exposureGlobalNames) != 0:
+                        raise WebIDLError("[Exposed] specified on both a "
+                                          "partial interface member and on the "
+                                          "partial interface itself",
+                                          [member.location, attr.location])
+                    member.addExtendedAttributes([attr])
+            else:
+                raise WebIDLError("Unknown extended attribute %s on partial "
+                                  "interface" % identifier,
+                                  [attr.location])
+
+    def finish(self, scope):
+        if self._finished:
+            return
+        self._finished = True
+        if (not self._haveSecureContextExtendedAttribute and
+            self._nonPartialInterfaceOrNamespace.getExtendedAttribute("SecureContext")):
+            # This gets propagated to all our members.
+            for member in self.members:
+                if member.getExtendedAttribute("SecureContext"):
+                    raise WebIDLError("[SecureContext] specified on both a "
+                                      "partial interface member and on the "
+                                      "non-partial interface",
+                                      [member.location,
+                                       self._nonPartialInterfaceOrNamespace.location])
+                member.addExtendedAttributes(
+                    [IDLExtendedAttribute(self._nonPartialInterfaceOrNamespace.location,
+                                          ("SecureContext",))])
+        # Need to make sure our non-partial interface or namespace gets
+        # finished so it can report cases when we only have partial
+        # interfaces/namespaces.
+        self._nonPartialInterfaceOrNamespace.finish(scope)
+
+    def validate(self):
+        pass
+
+
+def convertExposedAttrToGlobalNameSet(exposedAttr, targetSet):
+    assert len(targetSet) == 0
+    if exposedAttr.hasValue():
+        targetSet.add(exposedAttr.value())
+    else:
+        assert exposedAttr.hasArgs()
+        targetSet.update(exposedAttr.args())
+
+
+def globalNameSetToExposureSet(globalScope, nameSet, exposureSet):
+    for name in nameSet:
+        exposureSet.update(globalScope.globalNameMapping[name])
+
+
+class IDLInterfaceOrNamespace(IDLObjectWithScope, IDLExposureMixins):
+    def __init__(self, location, parentScope, name, parent, members,
+                 isKnownNonPartial):
+        assert isinstance(parentScope, IDLScope)
+        assert isinstance(name, IDLUnresolvedIdentifier)
+        assert isKnownNonPartial or not parent
+        assert isKnownNonPartial or len(members) == 0
+
+        self.parent = None
+        self._callback = False
+        self._finished = False
+        self.members = []
+        self.maplikeOrSetlikeOrIterable = None
+        self._partialInterfaces = []
+        self._extendedAttrDict = {}
+        # namedConstructors needs deterministic ordering because bindings code
+        # outputs the constructs in the order that namedConstructors enumerates
+        # them.
+        self.namedConstructors = list()
+        self.implementedInterfaces = set()
+        self._consequential = False
+        self._isKnownNonPartial = False
+        # self.interfacesBasedOnSelf is the set of interfaces that inherit from
+        # self or have self as a consequential interface, including self itself.
+        # Used for distinguishability checking.
+        self.interfacesBasedOnSelf = set([self])
+        # self.interfacesImplementingSelf is the set of interfaces that directly
+        # have self as a consequential interface
+        self.interfacesImplementingSelf = set()
+        self._hasChildInterfaces = False
+        self._isOnGlobalProtoChain = False
+        # Tracking of the number of reserved slots we need for our
+        # members and those of ancestor interfaces.
+        self.totalMembersInSlots = 0
+        # Tracking of the number of own own members we have in slots
+        self._ownMembersInSlots = 0
+        # If this is an iterator interface, we need to know what iterable
+        # interface we're iterating for in order to get its nativeType.
+        self.iterableInterface = None
+
+        IDLObjectWithScope.__init__(self, location, parentScope, name)
+        IDLExposureMixins.__init__(self, location)
+
+        if isKnownNonPartial:
+            self.setNonPartial(location, parent, members)
+
+    def ctor(self):
+        identifier = IDLUnresolvedIdentifier(self.location, "constructor",
+                                             allowForbidden=True)
+        try:
+            return self._lookupIdentifier(identifier)
+        except:
+            return None
+
+    def isIterable(self):
+        return (self.maplikeOrSetlikeOrIterable and
+                self.maplikeOrSetlikeOrIterable.isIterable())
+
+    def isIteratorInterface(self):
+        return self.iterableInterface is not None
+
+    def resolveIdentifierConflict(self, scope, identifier, originalObject, newObject):
+        assert isinstance(scope, IDLScope)
+        assert isinstance(originalObject, IDLInterfaceMember)
+        assert isinstance(newObject, IDLInterfaceMember)
+
+        retval = IDLScope.resolveIdentifierConflict(self, scope, identifier,
+                                                    originalObject, newObject)
+
+        # Might be a ctor, which isn't in self.members
+        if newObject in self.members:
+            self.members.remove(newObject)
+        return retval
+
+    def finish(self, scope):
+        if self._finished:
+            return
+
+        self._finished = True
+
+        if not self._isKnownNonPartial:
+            raise WebIDLError("Interface %s does not have a non-partial "
+                              "declaration" % self.identifier.name,
+                              [self.location])
+
+        IDLExposureMixins.finish(self, scope)
+
+        # Now go ahead and merge in our partial interfaces.
+        for partial in self._partialInterfaces:
+            partial.finish(scope)
+            self.addExtendedAttributes(partial.propagatedExtendedAttrs)
+            self.members.extend(partial.members)
+
+        # Generate maplike/setlike interface members. Since generated members
+        # need to be treated like regular interface members, do this before
+        # things like exposure setting.
+        for member in self.members:
+            if member.isMaplikeOrSetlikeOrIterable():
+                # Check that we only have one interface declaration (currently
+                # there can only be one maplike/setlike declaration per
+                # interface)
+                if self.maplikeOrSetlikeOrIterable:
+                    raise WebIDLError("%s declaration used on "
+                                      "interface that already has %s "
+                                      "declaration" %
+                                      (member.maplikeOrSetlikeOrIterableType,
+                                       self.maplikeOrSetlikeOrIterable.maplikeOrSetlikeOrIterableType),
+                                      [self.maplikeOrSetlikeOrIterable.location,
+                                       member.location])
+                self.maplikeOrSetlikeOrIterable = member
+                # If we've got a maplike or setlike declaration, we'll be building all of
+                # our required methods in Codegen. Generate members now.
+                self.maplikeOrSetlikeOrIterable.expand(self.members, self.isJSImplemented())
+
+        # Now that we've merged in our partial interfaces, set the
+        # _exposureGlobalNames on any members that don't have it set yet.  Note
+        # that any partial interfaces that had [Exposed] set have already set up
+        # _exposureGlobalNames on all the members coming from them, so this is
+        # just implementing the "members default to interface that defined them"
+        # and "partial interfaces default to interface they're a partial for"
+        # rules from the spec.
+        for m in self.members:
+            # If m, or the partial interface m came from, had [Exposed]
+            # specified, it already has a nonempty exposure global names set.
+            if len(m._exposureGlobalNames) == 0:
+                m._exposureGlobalNames.update(self._exposureGlobalNames)
+
+        assert not self.parent or isinstance(self.parent, IDLIdentifierPlaceholder)
+        parent = self.parent.finish(scope) if self.parent else None
+        if parent and isinstance(parent, IDLExternalInterface):
+            raise WebIDLError("%s inherits from %s which does not have "
+                              "a definition" %
+                              (self.identifier.name,
+                               self.parent.identifier.name),
+                              [self.location])
+        assert not parent or isinstance(parent, IDLInterface)
+
+        self.parent = parent
+
+        assert iter(self.members)
+
+        if self.isNamespace():
+            assert not self.parent
+            for m in self.members:
+                if m.isAttr() or m.isMethod():
+                    if m.isStatic():
+                        raise WebIDLError("Don't mark things explicitly static "
+                                          "in namespaces",
+                                          [self.location, m.location])
+                    # Just mark all our methods/attributes as static.  The other
+                    # option is to duplicate the relevant InterfaceMembers
+                    # production bits but modified to produce static stuff to
+                    # start with, but that sounds annoying.
+                    m.forceStatic()
+
+        if self.parent:
+            self.parent.finish(scope)
+            self.parent._hasChildInterfaces = True
+
+            self.totalMembersInSlots = self.parent.totalMembersInSlots
+
+            # Interfaces with [Global] or [PrimaryGlobal] must not
+            # have anything inherit from them
+            if (self.parent.getExtendedAttribute("Global") or
+                self.parent.getExtendedAttribute("PrimaryGlobal")):
+                # Note: This is not a self.parent.isOnGlobalProtoChain() check
+                # because ancestors of a [Global] interface can have other
+                # descendants.
+                raise WebIDLError("[Global] interface has another interface "
+                                  "inheriting from it",
+                                  [self.location, self.parent.location])
+
+            # Make sure that we're not exposed in places where our parent is not
+            if not self.exposureSet.issubset(self.parent.exposureSet):
+                raise WebIDLError("Interface %s is exposed in globals where its "
+                                  "parent interface %s is not exposed." %
+                                  (self.identifier.name,
+                                   self.parent.identifier.name),
+                                  [self.location, self.parent.location])
+
+            # Callbacks must not inherit from non-callbacks or inherit from
+            # anything that has consequential interfaces.
+            # XXXbz Can non-callbacks inherit from callbacks?  Spec issue pending.
+            # XXXbz Can callbacks have consequential interfaces?  Spec issue pending
+            if self.isCallback():
+                if not self.parent.isCallback():
+                    raise WebIDLError("Callback interface %s inheriting from "
+                                      "non-callback interface %s" %
+                                      (self.identifier.name,
+                                       self.parent.identifier.name),
+                                      [self.location, self.parent.location])
+            elif self.parent.isCallback():
+                raise WebIDLError("Non-callback interface %s inheriting from "
+                                  "callback interface %s" %
+                                  (self.identifier.name,
+                                   self.parent.identifier.name),
+                                  [self.location, self.parent.location])
+
+            # Interfaces which have interface objects can't inherit
+            # from [NoInterfaceObject] interfaces.
+            if (self.parent.getExtendedAttribute("NoInterfaceObject") and
+                not self.getExtendedAttribute("NoInterfaceObject")):
+                raise WebIDLError("Interface %s does not have "
+                                  "[NoInterfaceObject] but inherits from "
+                                  "interface %s which does" %
+                                  (self.identifier.name,
+                                   self.parent.identifier.name),
+                                  [self.location, self.parent.location])
+
+            # Interfaces that are not [SecureContext] can't inherit
+            # from [SecureContext] interfaces.
+            if (self.parent.getExtendedAttribute("SecureContext") and
+                not self.getExtendedAttribute("SecureContext")):
+                raise WebIDLError("Interface %s does not have "
+                                  "[SecureContext] but inherits from "
+                                  "interface %s which does" %
+                                  (self.identifier.name,
+                                   self.parent.identifier.name),
+                                  [self.location, self.parent.location])
+
+        for iface in self.implementedInterfaces:
+            iface.finish(scope)
+
+        cycleInGraph = self.findInterfaceLoopPoint(self)
+        if cycleInGraph:
+            raise WebIDLError("Interface %s has itself as ancestor or "
+                              "implemented interface" % self.identifier.name,
+                              [self.location, cycleInGraph.location])
+
+        if self.isCallback():
+            # "implements" should have made sure we have no
+            # consequential interfaces.
+            assert len(self.getConsequentialInterfaces()) == 0
+            # And that we're not consequential.
+            assert not self.isConsequential()
+
+        # Now resolve() and finish() our members before importing the
+        # ones from our implemented interfaces.
+
+        # resolve() will modify self.members, so we need to iterate
+        # over a copy of the member list here.
+        for member in list(self.members):
+            member.resolve(self)
+
+        for member in self.members:
+            member.finish(scope)
+
+        # Now that we've finished our members, which has updated their exposure
+        # sets, make sure they aren't exposed in places where we are not.
+        for member in self.members:
+            if not member.exposureSet.issubset(self.exposureSet):
+                raise WebIDLError("Interface member has larger exposure set "
+                                  "than the interface itself",
+                                  [member.location, self.location])
+
+        ctor = self.ctor()
+        if ctor is not None:
+            assert len(ctor._exposureGlobalNames) == 0
+            ctor._exposureGlobalNames.update(self._exposureGlobalNames)
+            ctor.finish(scope)
+
+        for ctor in self.namedConstructors:
+            assert len(ctor._exposureGlobalNames) == 0
+            ctor._exposureGlobalNames.update(self._exposureGlobalNames)
+            ctor.finish(scope)
+
+        # Make a copy of our member list, so things that implement us
+        # can get those without all the stuff we implement ourselves
+        # admixed.
+        self.originalMembers = list(self.members)
+
+        # Import everything from our consequential interfaces into
+        # self.members.  Sort our consequential interfaces by name
+        # just so we have a consistent order.
+        for iface in sorted(self.getConsequentialInterfaces(),
+                            cmp=cmp,
+                            key=lambda x: x.identifier.name):
+            # Flag the interface as being someone's consequential interface
+            iface.setIsConsequentialInterfaceOf(self)
+            # Verify that we're not exposed somewhere where iface is not exposed
+            if not self.exposureSet.issubset(iface.exposureSet):
+                raise WebIDLError("Interface %s is exposed in globals where its "
+                                  "consequential interface %s is not exposed." %
+                                  (self.identifier.name, iface.identifier.name),
+                                  [self.location, iface.location])
+
+            # If we have a maplike or setlike, and the consequential interface
+            # also does, throw an error.
+            if iface.maplikeOrSetlikeOrIterable and self.maplikeOrSetlikeOrIterable:
+                raise WebIDLError("Maplike/setlike/iterable interface %s cannot have "
+                                  "maplike/setlike/iterable interface %s as a "
+                                  "consequential interface" %
+                                  (self.identifier.name,
+                                   iface.identifier.name),
+                                  [self.maplikeOrSetlikeOrIterable.location,
+                                   iface.maplikeOrSetlikeOrIterable.location])
+            additionalMembers = iface.originalMembers
+            for additionalMember in additionalMembers:
+                for member in self.members:
+                    if additionalMember.identifier.name == member.identifier.name:
+                        raise WebIDLError(
+                            "Multiple definitions of %s on %s coming from 'implements' statements" %
+                            (member.identifier.name, self),
+                            [additionalMember.location, member.location])
+            self.members.extend(additionalMembers)
+            iface.interfacesImplementingSelf.add(self)
+
+        for ancestor in self.getInheritedInterfaces():
+            ancestor.interfacesBasedOnSelf.add(self)
+            if (ancestor.maplikeOrSetlikeOrIterable is not None and
+                self.maplikeOrSetlikeOrIterable is not None):
+                raise WebIDLError("Cannot have maplike/setlike on %s that "
+                                  "inherits %s, which is already "
+                                  "maplike/setlike" %
+                                  (self.identifier.name,
+                                   ancestor.identifier.name),
+                                  [self.maplikeOrSetlikeOrIterable.location,
+                                   ancestor.maplikeOrSetlikeOrIterable.location])
+            for ancestorConsequential in ancestor.getConsequentialInterfaces():
+                ancestorConsequential.interfacesBasedOnSelf.add(self)
+
+        # Deal with interfaces marked [Unforgeable], now that we have our full
+        # member list, except unforgeables pulled in from parents.  We want to
+        # do this before we set "originatingInterface" on our unforgeable
+        # members.
+        if self.getExtendedAttribute("Unforgeable"):
+            # Check that the interface already has all the things the
+            # spec would otherwise require us to synthesize and is
+            # missing the ones we plan to synthesize.
+            if not any(m.isMethod() and m.isStringifier() for m in self.members):
+                raise WebIDLError("Unforgeable interface %s does not have a "
+                                  "stringifier" % self.identifier.name,
+                                  [self.location])
+
+            for m in self.members:
+                if ((m.isMethod() and m.isJsonifier()) or
+                    m.identifier.name == "toJSON"):
+                    raise WebIDLError("Unforgeable interface %s has a "
+                                      "jsonifier so we won't be able to add "
+                                      "one ourselves" % self.identifier.name,
+                                      [self.location, m.location])
+
+                if m.identifier.name == "valueOf" and not m.isStatic():
+                    raise WebIDLError("Unforgeable interface %s has a valueOf "
+                                      "member so we won't be able to add one "
+                                      "ourselves" % self.identifier.name,
+                                      [self.location, m.location])
+
+        for member in self.members:
+            if ((member.isAttr() or member.isMethod()) and
+                member.isUnforgeable() and
+                not hasattr(member, "originatingInterface")):
+                member.originatingInterface = self
+
+        # Compute slot indices for our members before we pull in unforgeable
+        # members from our parent. Also, maplike/setlike declarations get a
+        # slot to hold their backing object.
+        for member in self.members:
+            if ((member.isAttr() and
+                 (member.getExtendedAttribute("StoreInSlot") or
+                  member.getExtendedAttribute("Cached"))) or
+                member.isMaplikeOrSetlike()):
+                if member.slotIndices is None:
+                    member.slotIndices = dict()
+                member.slotIndices[self.identifier.name] = self.totalMembersInSlots
+                self.totalMembersInSlots += 1
+                if member.getExtendedAttribute("StoreInSlot"):
+                    self._ownMembersInSlots += 1
+
+        if self.parent:
+            # Make sure we don't shadow any of the [Unforgeable] attributes on
+            # our ancestor interfaces.  We don't have to worry about
+            # consequential interfaces here, because those have already been
+            # imported into the relevant .members lists.  And we don't have to
+            # worry about anything other than our parent, because it has already
+            # imported its ancestors unforgeable attributes into its member
+            # list.
+            for unforgeableMember in (member for member in self.parent.members if
+                                      (member.isAttr() or member.isMethod()) and
+                                      member.isUnforgeable()):
+                shadows = [m for m in self.members if
+                           (m.isAttr() or m.isMethod()) and
+                           not m.isStatic() and
+                           m.identifier.name == unforgeableMember.identifier.name]
+                if len(shadows) != 0:
+                    locs = [unforgeableMember.location] + [s.location for s
+                                                           in shadows]
+                    raise WebIDLError("Interface %s shadows [Unforgeable] "
+                                      "members of %s" %
+                                      (self.identifier.name,
+                                       ancestor.identifier.name),
+                                      locs)
+                # And now just stick it in our members, since we won't be
+                # inheriting this down the proto chain.  If we really cared we
+                # could try to do something where we set up the unforgeable
+                # attributes/methods of ancestor interfaces, with their
+                # corresponding getters, on our interface, but that gets pretty
+                # complicated and seems unnecessary.
+                self.members.append(unforgeableMember)
+
+        # At this point, we have all of our members. If the current interface
+        # uses maplike/setlike, check for collisions anywhere in the current
+        # interface or higher in the inheritance chain.
+        if self.maplikeOrSetlikeOrIterable:
+            testInterface = self
+            isAncestor = False
+            while testInterface:
+                self.maplikeOrSetlikeOrIterable.checkCollisions(testInterface.members,
+                                                                isAncestor)
+                isAncestor = True
+                testInterface = testInterface.parent
+
+        # Ensure that there's at most one of each {named,indexed}
+        # {getter,setter,creator,deleter}, at most one stringifier,
+        # and at most one legacycaller.  Note that this last is not
+        # quite per spec, but in practice no one overloads
+        # legacycallers.  Also note that in practice we disallow
+        # indexed deleters, but it simplifies some other code to
+        # treat deleter analogously to getter/setter/creator by
+        # prefixing it with "named".
+        specialMembersSeen = {}
+        for member in self.members:
+            if not member.isMethod():
+                continue
+
+            if member.isGetter():
+                memberType = "getters"
+            elif member.isSetter():
+                memberType = "setters"
+            elif member.isCreator():
+                memberType = "creators"
+            elif member.isDeleter():
+                memberType = "deleters"
+            elif member.isStringifier():
+                memberType = "stringifiers"
+            elif member.isJsonifier():
+                memberType = "jsonifiers"
+            elif member.isLegacycaller():
+                memberType = "legacycallers"
+            else:
+                continue
+
+            if (memberType != "stringifiers" and memberType != "legacycallers" and
+                memberType != "jsonifiers"):
+                if member.isNamed():
+                    memberType = "named " + memberType
+                else:
+                    assert member.isIndexed()
+                    memberType = "indexed " + memberType
+
+            if memberType in specialMembersSeen:
+                raise WebIDLError("Multiple " + memberType + " on %s" % (self),
+                                  [self.location,
+                                   specialMembersSeen[memberType].location,
+                                   member.location])
+
+            specialMembersSeen[memberType] = member
+
+        if self.getExtendedAttribute("LegacyUnenumerableNamedProperties"):
+            # Check that we have a named getter.
+            if "named getters" not in specialMembersSeen:
+                raise WebIDLError(
+                    "Interface with [LegacyUnenumerableNamedProperties] does "
+                    "not have a named getter",
+                    [self.location])
+            ancestor = self.parent
+            while ancestor:
+                if ancestor.getExtendedAttribute("LegacyUnenumerableNamedProperties"):
+                    raise WebIDLError(
+                        "Interface with [LegacyUnenumerableNamedProperties] "
+                        "inherits from another interface with "
+                        "[LegacyUnenumerableNamedProperties]",
+                        [self.location, ancestor.location])
+                ancestor = ancestor.parent
+
+        if self._isOnGlobalProtoChain:
+            # Make sure we have no named setters, creators, or deleters
+            for memberType in ["setter", "creator", "deleter"]:
+                memberId = "named " + memberType + "s"
+                if memberId in specialMembersSeen:
+                    raise WebIDLError("Interface with [Global] has a named %s" %
+                                      memberType,
+                                      [self.location,
+                                       specialMembersSeen[memberId].location])
+            # Make sure we're not [OverrideBuiltins]
+            if self.getExtendedAttribute("OverrideBuiltins"):
+                raise WebIDLError("Interface with [Global] also has "
+                                  "[OverrideBuiltins]",
+                                  [self.location])
+            # Mark all of our ancestors as being on the global's proto chain too
+            parent = self.parent
+            while parent:
+                # Must not inherit from an interface with [OverrideBuiltins]
+                if parent.getExtendedAttribute("OverrideBuiltins"):
+                    raise WebIDLError("Interface with [Global] inherits from "
+                                      "interface with [OverrideBuiltins]",
+                                      [self.location, parent.location])
+                parent._isOnGlobalProtoChain = True
+                parent = parent.parent
+
+    def validate(self):
+        # We don't support consequential unforgeable interfaces.  Need to check
+        # this here, because in finish() an interface might not know yet that
+        # it's consequential.
+        if self.getExtendedAttribute("Unforgeable") and self.isConsequential():
+            raise WebIDLError(
+                "%s is an unforgeable consequential interface" %
+                self.identifier.name,
+                [self.location] +
+                list(i.location for i in
+                     (self.interfacesBasedOnSelf - {self})))
+
+        # We also don't support inheriting from unforgeable interfaces.
+        if self.getExtendedAttribute("Unforgeable") and self.hasChildInterfaces():
+            locations = ([self.location] +
+                         list(i.location for i in
+                              self.interfacesBasedOnSelf if i.parent == self))
+            raise WebIDLError("%s is an unforgeable ancestor interface" %
+                              self.identifier.name,
+                              locations)
+
+        indexedGetter = None
+        hasLengthAttribute = False
+        for member in self.members:
+            member.validate()
+
+            if self.isCallback() and member.getExtendedAttribute("Replaceable"):
+                raise WebIDLError("[Replaceable] used on an attribute on "
+                                  "interface %s which is a callback interface" %
+                                  self.identifier.name,
+                                  [self.location, member.location])
+
+            # Check that PutForwards refers to another attribute and that no
+            # cycles exist in forwarded assignments.  Also check for a
+            # integer-typed "length" attribute.
+            if member.isAttr():
+                if (member.identifier.name == "length" and
+                    member.type.isInteger()):
+                    hasLengthAttribute = True
+
+                iface = self
+                attr = member
+                putForwards = attr.getExtendedAttribute("PutForwards")
+                if putForwards and self.isCallback():
+                    raise WebIDLError("[PutForwards] used on an attribute "
+                                      "on interface %s which is a callback "
+                                      "interface" % self.identifier.name,
+                                      [self.location, member.location])
+
+                while putForwards is not None:
+                    forwardIface = attr.type.unroll().inner
+                    fowardAttr = None
+
+                    for forwardedMember in forwardIface.members:
+                        if (not forwardedMember.isAttr() or
+                            forwardedMember.identifier.name != putForwards[0]):
+                            continue
+                        if forwardedMember == member:
+                            raise WebIDLError("Cycle detected in forwarded "
+                                              "assignments for attribute %s on "
+                                              "%s" %
+                                              (member.identifier.name, self),
+                                              [member.location])
+                        fowardAttr = forwardedMember
+                        break
+
+                    if fowardAttr is None:
+                        raise WebIDLError("Attribute %s on %s forwards to "
+                                          "missing attribute %s" %
+                                          (attr.identifier.name, iface, putForwards),
+                                          [attr.location])
+
+                    iface = forwardIface
+                    attr = fowardAttr
+                    putForwards = attr.getExtendedAttribute("PutForwards")
+
+            # Check that the name of an [Alias] doesn't conflict with an
+            # interface member and whether we support indexed properties.
+            if member.isMethod():
+                if member.isGetter() and member.isIndexed():
+                    indexedGetter = member
+
+                for alias in member.aliases:
+                    if self.isOnGlobalProtoChain():
+                        raise WebIDLError("[Alias] must not be used on a "
+                                          "[Global] interface operation",
+                                          [member.location])
+                    if (member.getExtendedAttribute("Exposed") or
+                        member.getExtendedAttribute("ChromeOnly") or
+                        member.getExtendedAttribute("Pref") or
+                        member.getExtendedAttribute("Func") or
+                        member.getExtendedAttribute("SecureContext")):
+                        raise WebIDLError("[Alias] must not be used on a "
+                                          "conditionally exposed operation",
+                                          [member.location])
+                    if member.isStatic():
+                        raise WebIDLError("[Alias] must not be used on a "
+                                          "static operation",
+                                          [member.location])
+                    if member.isIdentifierLess():
+                        raise WebIDLError("[Alias] must not be used on an "
+                                          "identifierless operation",
+                                          [member.location])
+                    if member.isUnforgeable():
+                        raise WebIDLError("[Alias] must not be used on an "
+                                          "[Unforgeable] operation",
+                                          [member.location])
+                    for m in self.members:
+                        if m.identifier.name == alias:
+                            raise WebIDLError("[Alias=%s] has same name as "
+                                              "interface member" % alias,
+                                              [member.location, m.location])
+                        if m.isMethod() and m != member and alias in m.aliases:
+                            raise WebIDLError("duplicate [Alias=%s] definitions" %
+                                              alias,
+                                              [member.location, m.location])
+
+        if (self.getExtendedAttribute("Pref") and
+            self._exposureGlobalNames != set([self.parentScope.primaryGlobalName])):
+            raise WebIDLError("[Pref] used on an interface that is not %s-only" %
+                              self.parentScope.primaryGlobalName,
+                              [self.location])
+
+        # Conditional exposure makes no sense for interfaces with no
+        # interface object, unless they're navigator properties.
+        # And SecureContext makes sense for interfaces with no interface object,
+        # since it is also propagated to interface members.
+        if (self.isExposedConditionally(exclusions=["SecureContext"]) and
+            not self.hasInterfaceObject() and
+            not self.isNavigatorProperty()):
+            raise WebIDLError("Interface with no interface object is "
+                              "exposed conditionally",
+                              [self.location])
+
+        # Value iterators are only allowed on interfaces with indexed getters,
+        # and pair iterators are only allowed on interfaces without indexed
+        # getters.
+        if self.isIterable():
+            iterableDecl = self.maplikeOrSetlikeOrIterable
+            if iterableDecl.isValueIterator():
+                if not indexedGetter:
+                    raise WebIDLError("Interface with value iterator does not "
+                                      "support indexed properties",
+                                      [self.location])
+
+                if iterableDecl.valueType != indexedGetter.signatures()[0][0]:
+                    raise WebIDLError("Iterable type does not match indexed "
+                                      "getter type",
+                                      [iterableDecl.location,
+                                       indexedGetter.location])
+
+                if not hasLengthAttribute:
+                    raise WebIDLError('Interface with value iterator does not '
+                                      'have an integer-typed "length" attribute',
+                                      [self.location])
+            else:
+                assert iterableDecl.isPairIterator()
+                if indexedGetter:
+                    raise WebIDLError("Interface with pair iterator supports "
+                                      "indexed properties",
+                                      [self.location, iterableDecl.location,
+                                       indexedGetter.location])
+
+    def isExternal(self):
+        return False
+
+    def setIsConsequentialInterfaceOf(self, other):
+        self._consequential = True
+        self.interfacesBasedOnSelf.add(other)
+
+    def isConsequential(self):
+        return self._consequential
+
+    def setCallback(self, value):
+        self._callback = value
+
+    def isCallback(self):
+        return self._callback
+
+    def isSingleOperationInterface(self):
+        assert self.isCallback() or self.isJSImplemented()
+        return (
+            # JS-implemented things should never need the
+            # this-handling weirdness of single-operation interfaces.
+            not self.isJSImplemented() and
+            # Not inheriting from another interface
+            not self.parent and
+            # No consequential interfaces
+            len(self.getConsequentialInterfaces()) == 0 and
+            # No attributes of any kinds
+            not any(m.isAttr() for m in self.members) and
+            # There is at least one regular operation, and all regular
+            # operations have the same identifier
+            len(set(m.identifier.name for m in self.members if
+                    m.isMethod() and not m.isStatic())) == 1)
+
+    def inheritanceDepth(self):
+        depth = 0
+        parent = self.parent
+        while parent:
+            depth = depth + 1
+            parent = parent.parent
+        return depth
+
+    def hasConstants(self):
+        return any(m.isConst() for m in self.members)
+
+    def hasInterfaceObject(self):
+        if self.isCallback():
+            return self.hasConstants()
+        return not hasattr(self, "_noInterfaceObject")
+
+    def hasInterfacePrototypeObject(self):
+        return (not self.isCallback() and not self.isNamespace()
+                and self.getUserData('hasConcreteDescendant', False))
+
+    def addImplementedInterface(self, implementedInterface):
+        assert(isinstance(implementedInterface, IDLInterface))
+        self.implementedInterfaces.add(implementedInterface)
+
+    def getInheritedInterfaces(self):
+        """
+        Returns a list of the interfaces this interface inherits from
+        (not including this interface itself).  The list is in order
+        from most derived to least derived.
+        """
+        assert(self._finished)
+        if not self.parent:
+            return []
+        parentInterfaces = self.parent.getInheritedInterfaces()
+        parentInterfaces.insert(0, self.parent)
+        return parentInterfaces
+
+    def getConsequentialInterfaces(self):
+        assert(self._finished)
+        # The interfaces we implement directly
+        consequentialInterfaces = set(self.implementedInterfaces)
+
+        # And their inherited interfaces
+        for iface in self.implementedInterfaces:
+            consequentialInterfaces |= set(iface.getInheritedInterfaces())
+
+        # And now collect up the consequential interfaces of all of those
+        temp = set()
+        for iface in consequentialInterfaces:
+            temp |= iface.getConsequentialInterfaces()
+
+        return consequentialInterfaces | temp
+
+    def findInterfaceLoopPoint(self, otherInterface):
+        """
+        Finds an interface, amongst our ancestors and consequential interfaces,
+        that inherits from otherInterface or implements otherInterface
+        directly.  If there is no such interface, returns None.
+        """
+        if self.parent:
+            if self.parent == otherInterface:
+                return self
+            loopPoint = self.parent.findInterfaceLoopPoint(otherInterface)
+            if loopPoint:
+                return loopPoint
+        if otherInterface in self.implementedInterfaces:
+            return self
+        for iface in self.implementedInterfaces:
+            loopPoint = iface.findInterfaceLoopPoint(otherInterface)
+            if loopPoint:
+                return loopPoint
+        return None
+
+    def getExtendedAttribute(self, name):
+        return self._extendedAttrDict.get(name, None)
+
+    def setNonPartial(self, location, parent, members):
+        assert not parent or isinstance(parent, IDLIdentifierPlaceholder)
+        if self._isKnownNonPartial:
+            raise WebIDLError("Two non-partial definitions for the "
+                              "same %s" %
+                              ("interface" if self.isInterface()
+                               else "namespace"),
+                              [location, self.location])
+        self._isKnownNonPartial = True
+        # Now make it look like we were parsed at this new location, since
+        # that's the place where the interface is "really" defined
+        self.location = location
+        assert not self.parent
+        self.parent = parent
+        # Put the new members at the beginning
+        self.members = members + self.members
+
+    def addPartialInterface(self, partial):
+        assert self.identifier.name == partial.identifier.name
+        self._partialInterfaces.append(partial)
+
+    def getJSImplementation(self):
+        classId = self.getExtendedAttribute("JSImplementation")
+        if not classId:
+            return classId
+        assert isinstance(classId, list)
+        assert len(classId) == 1
+        return classId[0]
+
+    def isJSImplemented(self):
+        return bool(self.getJSImplementation())
+
+    def isProbablyShortLivingObject(self):
+        current = self
+        while current:
+            if current.getExtendedAttribute("ProbablyShortLivingObject"):
+                return True
+            current = current.parent
+        return False
+
+    def isNavigatorProperty(self):
+        naviProp = self.getExtendedAttribute("NavigatorProperty")
+        if not naviProp:
+            return False
+        assert len(naviProp) == 1
+        assert isinstance(naviProp, list)
+        assert len(naviProp[0]) != 0
+        return True
+
+    def getNavigatorProperty(self):
+        naviProp = self.getExtendedAttribute("NavigatorProperty")
+        if not naviProp:
+            return None
+        assert len(naviProp) == 1
+        assert isinstance(naviProp, list)
+        assert len(naviProp[0]) != 0
+        conditionExtendedAttributes = self._extendedAttrDict.viewkeys() & IDLInterfaceOrNamespace.conditionExtendedAttributes
+        attr = IDLAttribute(self.location,
+                            IDLUnresolvedIdentifier(BuiltinLocation("<auto-generated-identifier>"), naviProp[0]),
+                            IDLUnresolvedType(self.location, IDLUnresolvedIdentifier(self.location, self.identifier.name)),
+                            True,
+                            extendedAttrDict={ a: self._extendedAttrDict[a] for a in conditionExtendedAttributes },
+                            navigatorObjectGetter=True)
+        attr._exposureGlobalNames = self._exposureGlobalNames
+        # We're abusing Constant a little bit here, because we need Cached. The
+        # getter will create a new object every time, but we're never going to
+        # clear the cached value.
+        extendedAttrs = [ IDLExtendedAttribute(self.location, ("Throws", )),
+                          IDLExtendedAttribute(self.location, ("Cached", )),
+                          IDLExtendedAttribute(self.location, ("Constant", )) ]
+        attr.addExtendedAttributes(extendedAttrs)
+        return attr
+
+    def hasChildInterfaces(self):
+        return self._hasChildInterfaces
+
+    def isOnGlobalProtoChain(self):
+        return self._isOnGlobalProtoChain
+
+    def _getDependentObjects(self):
+        deps = set(self.members)
+        deps.update(self.implementedInterfaces)
+        if self.parent:
+            deps.add(self.parent)
+        return deps
+
+    def hasMembersInSlots(self):
+        return self._ownMembersInSlots != 0
+
+    conditionExtendedAttributes = [ "Pref", "ChromeOnly", "Func", "AvailableIn",
+                                    "SecureContext",
+                                    "CheckAnyPermissions",
+                                    "CheckAllPermissions" ]
+    def isExposedConditionally(self, exclusions=[]):
+        return any(((not a in exclusions) and self.getExtendedAttribute(a)) for a in self.conditionExtendedAttributes)
+
+class IDLInterface(IDLInterfaceOrNamespace):
+    def __init__(self, location, parentScope, name, parent, members,
+                 isKnownNonPartial):
+        IDLInterfaceOrNamespace.__init__(self, location, parentScope, name,
+                                         parent, members, isKnownNonPartial)
+
+    def __str__(self):
+        return "Interface '%s'" % self.identifier.name
+
+    def isInterface(self):
+        return True
+
+    def addExtendedAttributes(self, attrs):
+        for attr in attrs:
+            identifier = attr.identifier()
+
+            # Special cased attrs
+            if identifier == "TreatNonCallableAsNull":
+                raise WebIDLError("TreatNonCallableAsNull cannot be specified on interfaces",
+                                  [attr.location, self.location])
+            if identifier == "TreatNonObjectAsNull":
+                raise WebIDLError("TreatNonObjectAsNull cannot be specified on interfaces",
+                                  [attr.location, self.location])
+            elif identifier == "NoInterfaceObject":
+                if not attr.noArguments():
+                    raise WebIDLError("[NoInterfaceObject] must take no arguments",
+                                      [attr.location])
+
+                if self.ctor():
+                    raise WebIDLError("Constructor and NoInterfaceObject are incompatible",
+                                      [self.location])
+
+                self._noInterfaceObject = True
+            elif identifier == "Constructor" or identifier == "NamedConstructor" or identifier == "ChromeConstructor":
+                if identifier == "Constructor" and not self.hasInterfaceObject():
+                    raise WebIDLError(str(identifier) + " and NoInterfaceObject are incompatible",
+                                      [self.location])
+
+                if identifier == "NamedConstructor" and not attr.hasValue():
+                    raise WebIDLError("NamedConstructor must either take an identifier or take a named argument list",
+                                      [attr.location])
+
+                if identifier == "ChromeConstructor" and not self.hasInterfaceObject():
+                    raise WebIDLError(str(identifier) + " and NoInterfaceObject are incompatible",
+                                      [self.location])
+
+                args = attr.args() if attr.hasArgs() else []
+
+                if self.identifier.name == "Promise":
+                    promiseType = BuiltinTypes[IDLBuiltinType.Types.any]
+                else:
+                    promiseType = None
+                retType = IDLWrapperType(self.location, self, promiseType)
+
+                if identifier == "Constructor" or identifier == "ChromeConstructor":
+                    name = "constructor"
+                    allowForbidden = True
+                else:
+                    name = attr.value()
+                    allowForbidden = False
+
+                methodIdentifier = IDLUnresolvedIdentifier(self.location, name,
+                                                           allowForbidden=allowForbidden)
+
+                method = IDLMethod(self.location, methodIdentifier, retType,
+                                   args, static=True)
+                # Constructors are always NewObject and are always
+                # assumed to be able to throw (since there's no way to
+                # indicate otherwise) and never have any other
+                # extended attributes.
+                method.addExtendedAttributes(
+                    [IDLExtendedAttribute(self.location, ("NewObject",)),
+                     IDLExtendedAttribute(self.location, ("Throws",))])
+                if identifier == "ChromeConstructor":
+                    method.addExtendedAttributes(
+                        [IDLExtendedAttribute(self.location, ("ChromeOnly",))])
+
+                if identifier == "Constructor" or identifier == "ChromeConstructor":
+                    method.resolve(self)
+                else:
+                    # We need to detect conflicts for NamedConstructors across
+                    # interfaces. We first call resolve on the parentScope,
+                    # which will merge all NamedConstructors with the same
+                    # identifier accross interfaces as overloads.
+                    method.resolve(self.parentScope)
+
+                    # Then we look up the identifier on the parentScope. If the
+                    # result is the same as the method we're adding then it
+                    # hasn't been added as an overload and it's the first time
+                    # we've encountered a NamedConstructor with that identifier.
+                    # If the result is not the same as the method we're adding
+                    # then it has been added as an overload and we need to check
+                    # whether the result is actually one of our existing
+                    # NamedConstructors.
+                    newMethod = self.parentScope.lookupIdentifier(method.identifier)
+                    if newMethod == method:
+                        self.namedConstructors.append(method)
+                    elif newMethod not in self.namedConstructors:
+                        raise WebIDLError("NamedConstructor conflicts with a NamedConstructor of a different interface",
+                                          [method.location, newMethod.location])
+            elif (identifier == "ArrayClass"):
+                if not attr.noArguments():
+                    raise WebIDLError("[ArrayClass] must take no arguments",
+                                      [attr.location])
+                if self.parent:
+                    raise WebIDLError("[ArrayClass] must not be specified on "
+                                      "an interface with inherited interfaces",
+                                      [attr.location, self.location])
+            elif (identifier == "ExceptionClass"):
+                if not attr.noArguments():
+                    raise WebIDLError("[ExceptionClass] must take no arguments",
+                                      [attr.location])
+                if self.parent:
+                    raise WebIDLError("[ExceptionClass] must not be specified on "
+                                      "an interface with inherited interfaces",
+                                      [attr.location, self.location])
+            elif identifier == "Global":
+                if attr.hasValue():
+                    self.globalNames = [attr.value()]
+                elif attr.hasArgs():
+                    self.globalNames = attr.args()
+                else:
+                    self.globalNames = [self.identifier.name]
+                self.parentScope.globalNames.update(self.globalNames)
+                for globalName in self.globalNames:
+                    self.parentScope.globalNameMapping[globalName].add(self.identifier.name)
+                self._isOnGlobalProtoChain = True
+            elif identifier == "PrimaryGlobal":
+                if not attr.noArguments():
+                    raise WebIDLError("[PrimaryGlobal] must take no arguments",
+                                      [attr.location])
+                if self.parentScope.primaryGlobalAttr is not None:
+                    raise WebIDLError(
+                        "[PrimaryGlobal] specified twice",
+                        [attr.location,
+                         self.parentScope.primaryGlobalAttr.location])
+                self.parentScope.primaryGlobalAttr = attr
+                self.parentScope.primaryGlobalName = self.identifier.name
+                self.parentScope.globalNames.add(self.identifier.name)
+                self.parentScope.globalNameMapping[self.identifier.name].add(self.identifier.name)
+                self._isOnGlobalProtoChain = True
+            elif identifier == "SecureContext":
+                if not attr.noArguments():
+                    raise WebIDLError("[%s] must take no arguments" % identifier,
+                                      [attr.location])
+                # This gets propagated to all our members.
+                for member in self.members:
+                    if member.getExtendedAttribute("SecureContext"):
+                        raise WebIDLError("[SecureContext] specified on both "
+                                          "an interface member and on the "
+                                          "interface itself",
+                                          [member.location, attr.location])
+                    member.addExtendedAttributes([attr])
+            elif (identifier == "NeedResolve" or
+                  identifier == "OverrideBuiltins" or
+                  identifier == "ChromeOnly" or
+                  identifier == "Unforgeable" or
+                  identifier == "UnsafeInPrerendering" or
+                  identifier == "LegacyEventInit" or
+                  identifier == "ProbablyShortLivingObject" or
+                  identifier == "LegacyUnenumerableNamedProperties" or
+                  identifier == "NonOrdinaryGetPrototypeOf"):
+                # Known extended attributes that do not take values
+                if not attr.noArguments():
+                    raise WebIDLError("[%s] must take no arguments" % identifier,
+                                      [attr.location])
+            elif identifier == "Exposed":
+                convertExposedAttrToGlobalNameSet(attr,
+                                                  self._exposureGlobalNames)
+            elif (identifier == "Pref" or
+                  identifier == "JSImplementation" or
+                  identifier == "HeaderFile" or
+                  identifier == "NavigatorProperty" or
+                  identifier == "Func" or
+                  identifier == "Deprecated"):
+                # Known extended attributes that take a string value
+                if not attr.hasValue():
+                    raise WebIDLError("[%s] must have a value" % identifier,
+                                      [attr.location])
+            else:
+                raise WebIDLError("Unknown extended attribute %s on interface" % identifier,
+                                  [attr.location])
+
+            attrlist = attr.listValue()
+            self._extendedAttrDict[identifier] = attrlist if len(attrlist) else True
+
+
+class IDLNamespace(IDLInterfaceOrNamespace):
+    def __init__(self, location, parentScope, name, members, isKnownNonPartial):
+        IDLInterfaceOrNamespace.__init__(self, location, parentScope, name,
+                                         None, members, isKnownNonPartial)
+
+    def __str__(self):
+        return "Namespace '%s'" % self.identifier.name
+
+    def isNamespace(self):
+        return True
+
+    def addExtendedAttributes(self, attrs):
+        # The set of things namespaces support is small enough it's simpler
+        # to factor out into a separate method than it is to sprinkle
+        # isNamespace() checks all through
+        # IDLInterfaceOrNamespace.addExtendedAttributes.
+        for attr in attrs:
+            identifier = attr.identifier()
+
+            if identifier == "Exposed":
+                convertExposedAttrToGlobalNameSet(attr,
+                                                  self._exposureGlobalNames)
+            elif identifier == "ClassString":
+                # Takes a string value to override the default "Object" if
+                # desired.
+                if not attr.hasValue():
+                    raise WebIDLError("[%s] must have a value" % identifier,
+                                      [attr.location])
+            elif identifier == "ProtoObjectHack":
+                if not attr.noArguments():
+                    raise WebIDLError("[%s] must not have arguments" % identifier,
+                                      [attr.location])
+            else:
+                raise WebIDLError("Unknown extended attribute %s on namespace" %
+                                  identifier,
+                                  [attr.location])
+
+            attrlist = attr.listValue()
+            self._extendedAttrDict[identifier] = attrlist if len(attrlist) else True
+
+
+class IDLDictionary(IDLObjectWithScope):
+    def __init__(self, location, parentScope, name, parent, members):
+        assert isinstance(parentScope, IDLScope)
+        assert isinstance(name, IDLUnresolvedIdentifier)
+        assert not parent or isinstance(parent, IDLIdentifierPlaceholder)
+
+        self.parent = parent
+        self._finished = False
+        self.members = list(members)
+
+        IDLObjectWithScope.__init__(self, location, parentScope, name)
+
+    def __str__(self):
+        return "Dictionary '%s'" % self.identifier.name
+
+    def isDictionary(self):
+        return True
+
+    def canBeEmpty(self):
+        """
+        Returns true if this dictionary can be empty (that is, it has no
+        required members and neither do any of its ancestors).
+        """
+        return (all(member.optional for member in self.members) and
+                (not self.parent or self.parent.canBeEmpty()))
+
+    def finish(self, scope):
+        if self._finished:
+            return
+
+        self._finished = True
+
+        if self.parent:
+            assert isinstance(self.parent, IDLIdentifierPlaceholder)
+            oldParent = self.parent
+            self.parent = self.parent.finish(scope)
+            if not isinstance(self.parent, IDLDictionary):
+                raise WebIDLError("Dictionary %s has parent that is not a dictionary" %
+                                  self.identifier.name,
+                                  [oldParent.location, self.parent.location])
+
+            # Make sure the parent resolves all its members before we start
+            # looking at them.
+            self.parent.finish(scope)
+
+        for member in self.members:
+            member.resolve(self)
+            if not member.isComplete():
+                member.complete(scope)
+                assert member.type.isComplete()
+
+        # Members of a dictionary are sorted in lexicographic order
+        self.members.sort(cmp=cmp, key=lambda x: x.identifier.name)
+
+        inheritedMembers = []
+        ancestor = self.parent
+        while ancestor:
+            if ancestor == self:
+                raise WebIDLError("Dictionary %s has itself as an ancestor" %
+                                  self.identifier.name,
+                                  [self.identifier.location])
+            inheritedMembers.extend(ancestor.members)
+            ancestor = ancestor.parent
+
+        # Catch name duplication
+        for inheritedMember in inheritedMembers:
+            for member in self.members:
+                if member.identifier.name == inheritedMember.identifier.name:
+                    raise WebIDLError("Dictionary %s has two members with name %s" %
+                                      (self.identifier.name, member.identifier.name),
+                                      [member.location, inheritedMember.location])
+
+    def validate(self):
+        def typeContainsDictionary(memberType, dictionary):
+            """
+            Returns a tuple whose:
+
+                - First element is a Boolean value indicating whether
+                  memberType contains dictionary.
+
+                - Second element is:
+                    A list of locations that leads from the type that was passed in
+                    the memberType argument, to the dictionary being validated,
+                    if the boolean value in the first element is True.
+
+                    None, if the boolean value in the first element is False.
+            """
+
+            if (memberType.nullable() or
+                memberType.isSequence() or
+                memberType.isMozMap()):
+                return typeContainsDictionary(memberType.inner, dictionary)
+
+            if memberType.isDictionary():
+                if memberType.inner == dictionary:
+                    return (True, [memberType.location])
+
+                (contains, locations) = dictionaryContainsDictionary(memberType.inner,
+                                                                     dictionary)
+                if contains:
+                    return (True, [memberType.location] + locations)
+
+            if memberType.isUnion():
+                for member in memberType.flatMemberTypes:
+                    (contains, locations) = typeContainsDictionary(member, dictionary)
+                    if contains:
+                        return (True, locations)
+
+            return (False, None)
+
+        def dictionaryContainsDictionary(dictMember, dictionary):
+            for member in dictMember.members:
+                (contains, locations) = typeContainsDictionary(member.type, dictionary)
+                if contains:
+                    return (True, [member.location] + locations)
+
+            if dictMember.parent:
+                if dictMember.parent == dictionary:
+                    return (True, [dictMember.location])
+                else:
+                    (contains, locations) = dictionaryContainsDictionary(dictMember.parent, dictionary)
+                    if contains:
+                        return (True, [dictMember.location] + locations)
+
+            return (False, None)
+
+        for member in self.members:
+            if member.type.isDictionary() and member.type.nullable():
+                raise WebIDLError("Dictionary %s has member with nullable "
+                                  "dictionary type" % self.identifier.name,
+                                  [member.location])
+            (contains, locations) = typeContainsDictionary(member.type, self)
+            if contains:
+                raise WebIDLError("Dictionary %s has member with itself as type." %
+                                  self.identifier.name,
+                                  [member.location] + locations)
+
+    def addExtendedAttributes(self, attrs):
+        assert len(attrs) == 0
+
+    def _getDependentObjects(self):
+        deps = set(self.members)
+        if (self.parent):
+            deps.add(self.parent)
+        return deps
+
+
+class IDLEnum(IDLObjectWithIdentifier):
+    def __init__(self, location, parentScope, name, values):
+        assert isinstance(parentScope, IDLScope)
+        assert isinstance(name, IDLUnresolvedIdentifier)
+
+        if len(values) != len(set(values)):
+            raise WebIDLError("Enum %s has multiple identical strings" % name.name,
+                              [location])
+
+        IDLObjectWithIdentifier.__init__(self, location, parentScope, name)
+        self._values = values
+
+    def values(self):
+        return self._values
+
+    def finish(self, scope):
+        pass
+
+    def validate(self):
+        pass
+
+    def isEnum(self):
+        return True
+
+    def addExtendedAttributes(self, attrs):
+        assert len(attrs) == 0
+
+    def _getDependentObjects(self):
+        return set()
+
+
+class IDLType(IDLObject):
+    Tags = enum(
+        # The integer types
+        'int8',
+        'uint8',
+        'int16',
+        'uint16',
+        'int32',
+        'uint32',
+        'int64',
+        'uint64',
+        # Additional primitive types
+        'bool',
+        'unrestricted_float',
+        'float',
+        'unrestricted_double',
+        # "double" last primitive type to match IDLBuiltinType
+        'double',
+        # Other types
+        'any',
+        'domstring',
+        'bytestring',
+        'usvstring',
+        'object',
+        'date',
+        'void',
+        # Funny stuff
+        'interface',
+        'dictionary',
+        'enum',
+        'callback',
+        'union',
+        'sequence',
+        'mozmap'
+        )
+
+    def __init__(self, location, name):
+        IDLObject.__init__(self, location)
+        self.name = name
+        self.builtin = False
+
+    def __eq__(self, other):
+        return other and self.builtin == other.builtin and self.name == other.name
+
+    def __ne__(self, other):
+        return not self == other
+
+    def __str__(self):
+        return str(self.name)
+
+    def isType(self):
+        return True
+
+    def nullable(self):
+        return False
+
+    def isPrimitive(self):
+        return False
+
+    def isBoolean(self):
+        return False
+
+    def isNumeric(self):
+        return False
+
+    def isString(self):
+        return False
+
+    def isByteString(self):
+        return False
+
+    def isDOMString(self):
+        return False
+
+    def isUSVString(self):
+        return False
+
+    def isVoid(self):
+        return self.name == "Void"
+
+    def isSequence(self):
+        return False
+
+    def isMozMap(self):
+        return False
+
+    def isArrayBuffer(self):
+        return False
+
+    def isArrayBufferView(self):
+        return False
+
+    def isSharedArrayBuffer(self):
+        return False
+
+    def isTypedArray(self):
+        return False
+
+    def isCallbackInterface(self):
+        return False
+
+    def isNonCallbackInterface(self):
+        return False
+
+    def isGeckoInterface(self):
+        """ Returns a boolean indicating whether this type is an 'interface'
+            type that is implemented in Gecko. At the moment, this returns
+            true for all interface types that are not types from the TypedArray
+            spec."""
+        return self.isInterface() and not self.isSpiderMonkeyInterface()
+
+    def isSpiderMonkeyInterface(self):
+        """ Returns a boolean indicating whether this type is an 'interface'
+            type that is implemented in Spidermonkey.  At the moment, this
+            only returns true for the types from the TypedArray spec. """
+        return self.isInterface() and (self.isArrayBuffer() or
+                                       self.isArrayBufferView() or
+                                       self.isSharedArrayBuffer() or
+                                       self.isTypedArray())
+
+    def isDictionary(self):
+        return False
+
+    def isInterface(self):
+        return False
+
+    def isAny(self):
+        return self.tag() == IDLType.Tags.any
+
+    def isDate(self):
+        return self.tag() == IDLType.Tags.date
+
+    def isObject(self):
+        return self.tag() == IDLType.Tags.object
+
+    def isPromise(self):
+        return False
+
+    def isComplete(self):
+        return True
+
+    def includesRestrictedFloat(self):
+        return False
+
+    def isFloat(self):
+        return False
+
+    def isUnrestricted(self):
+        # Should only call this on float types
+        assert self.isFloat()
+
+    def isSerializable(self):
+        return False
+
+    def tag(self):
+        assert False  # Override me!
+
+    def treatNonCallableAsNull(self):
+        assert self.tag() == IDLType.Tags.callback
+        return self.nullable() and self.inner.callback._treatNonCallableAsNull
+
+    def treatNonObjectAsNull(self):
+        assert self.tag() == IDLType.Tags.callback
+        return self.nullable() and self.inner.callback._treatNonObjectAsNull
+
+    def addExtendedAttributes(self, attrs):
+        assert len(attrs) == 0
+
+    def resolveType(self, parentScope):
+        pass
+
+    def unroll(self):
+        return self
+
+    def isDistinguishableFrom(self, other):
+        raise TypeError("Can't tell whether a generic type is or is not "
+                        "distinguishable from other things")
+
+    def isExposedInAllOf(self, exposureSet):
+        return True
+
+
+class IDLUnresolvedType(IDLType):
+    """
+        Unresolved types are interface types
+    """
+
+    def __init__(self, location, name, promiseInnerType=None):
+        IDLType.__init__(self, location, name)
+        self._promiseInnerType = promiseInnerType
+
+    def isComplete(self):
+        return False
+
+    def complete(self, scope):
+        obj = None
+        try:
+            obj = scope._lookupIdentifier(self.name)
+        except:
+            raise WebIDLError("Unresolved type '%s'." % self.name,
+                              [self.location])
+
+        assert obj
+        if obj.isType():
+            print obj
+        assert not obj.isType()
+        if obj.isTypedef():
+            assert self.name.name == obj.identifier.name
+            typedefType = IDLTypedefType(self.location, obj.innerType,
+                                         obj.identifier)
+            assert not typedefType.isComplete()
+            return typedefType.complete(scope)
+        elif obj.isCallback() and not obj.isInterface():
+            assert self.name.name == obj.identifier.name
+            return IDLCallbackType(self.location, obj)
+
+        if self._promiseInnerType and not self._promiseInnerType.isComplete():
+            self._promiseInnerType = self._promiseInnerType.complete(scope)
+
+        name = self.name.resolve(scope, None)
+        return IDLWrapperType(self.location, obj, self._promiseInnerType)
+
+    def isDistinguishableFrom(self, other):
+        raise TypeError("Can't tell whether an unresolved type is or is not "
+                        "distinguishable from other things")
+
+
+class IDLParameterizedType(IDLType):
+    def __init__(self, location, name, innerType):
+        IDLType.__init__(self, location, name)
+        self.builtin = False
+        self.inner = innerType
+
+    def includesRestrictedFloat(self):
+        return self.inner.includesRestrictedFloat()
+
+    def resolveType(self, parentScope):
+        assert isinstance(parentScope, IDLScope)
+        self.inner.resolveType(parentScope)
+
+    def isComplete(self):
+        return self.inner.isComplete()
+
+    def unroll(self):
+        return self.inner.unroll()
+
+    def _getDependentObjects(self):
+        return self.inner._getDependentObjects()
+
+
+class IDLNullableType(IDLParameterizedType):
+    def __init__(self, location, innerType):
+        assert not innerType.isVoid()
+        assert not innerType == BuiltinTypes[IDLBuiltinType.Types.any]
+
+        name = innerType.name
+        if innerType.isComplete():
+            name += "OrNull"
+        IDLParameterizedType.__init__(self, location, name, innerType)
+
+    def __eq__(self, other):
+        return isinstance(other, IDLNullableType) and self.inner == other.inner
+
+    def __str__(self):
+        return self.inner.__str__() + "OrNull"
+
+    def nullable(self):
+        return True
+
+    def isCallback(self):
+        return self.inner.isCallback()
+
+    def isPrimitive(self):
+        return self.inner.isPrimitive()
+
+    def isBoolean(self):
+        return self.inner.isBoolean()
+
+    def isNumeric(self):
+        return self.inner.isNumeric()
+
+    def isString(self):
+        return self.inner.isString()
+
+    def isByteString(self):
+        return self.inner.isByteString()
+
+    def isDOMString(self):
+        return self.inner.isDOMString()
+
+    def isUSVString(self):
+        return self.inner.isUSVString()
+
+    def isFloat(self):
+        return self.inner.isFloat()
+
+    def isUnrestricted(self):
+        return self.inner.isUnrestricted()
+
+    def isInteger(self):
+        return self.inner.isInteger()
+
+    def isVoid(self):
+        return False
+
+    def isSequence(self):
+        return self.inner.isSequence()
+
+    def isMozMap(self):
+        return self.inner.isMozMap()
+
+    def isArrayBuffer(self):
+        return self.inner.isArrayBuffer()
+
+    def isArrayBufferView(self):
+        return self.inner.isArrayBufferView()
+
+    def isSharedArrayBuffer(self):
+        return self.inner.isSharedArrayBuffer()
+
+    def isTypedArray(self):
+        return self.inner.isTypedArray()
+
+    def isDictionary(self):
+        return self.inner.isDictionary()
+
+    def isInterface(self):
+        return self.inner.isInterface()
+
+    def isPromise(self):
+        return self.inner.isPromise()
+
+    def isCallbackInterface(self):
+        return self.inner.isCallbackInterface()
+
+    def isNonCallbackInterface(self):
+        return self.inner.isNonCallbackInterface()
+
+    def isEnum(self):
+        return self.inner.isEnum()
+
+    def isUnion(self):
+        return self.inner.isUnion()
+
+    def isSerializable(self):
+        return self.inner.isSerializable()
+
+    def tag(self):
+        return self.inner.tag()
+
+    def complete(self, scope):
+        self.inner = self.inner.complete(scope)
+        if self.inner.nullable():
+            raise WebIDLError("The inner type of a nullable type must not be "
+                              "a nullable type",
+                              [self.location, self.inner.location])
+        if self.inner.isUnion():
+            if self.inner.hasNullableType:
+                raise WebIDLError("The inner type of a nullable type must not "
+                                  "be a union type that itself has a nullable "
+                                  "type as a member type", [self.location])
+
+        self.name = self.inner.name + "OrNull"
+        return self
+
+    def isDistinguishableFrom(self, other):
+        if (other.nullable() or (other.isUnion() and other.hasNullableType) or
+            other.isDictionary()):
+            # Can't tell which type null should become
+            return False
+        return self.inner.isDistinguishableFrom(other)
+
+
+class IDLSequenceType(IDLParameterizedType):
+    def __init__(self, location, parameterType):
+        assert not parameterType.isVoid()
+
+        IDLParameterizedType.__init__(self, location, parameterType.name, parameterType)
+        # Need to set self.name up front if our inner type is already complete,
+        # since in that case our .complete() won't be called.
+        if self.inner.isComplete():
+            self.name = self.inner.name + "Sequence"
+
+    def __eq__(self, other):
+        return isinstance(other, IDLSequenceType) and self.inner == other.inner
+
+    def __str__(self):
+        return self.inner.__str__() + "Sequence"
+
+    def nullable(self):
+        return False
+
+    def isPrimitive(self):
+        return False
+
+    def isString(self):
+        return False
+
+    def isByteString(self):
+        return False
+
+    def isDOMString(self):
+        return False
+
+    def isUSVString(self):
+        return False
+
+    def isVoid(self):
+        return False
+
+    def isSequence(self):
+        return True
+
+    def isDictionary(self):
+        return False
+
+    def isInterface(self):
+        return False
+
+    def isEnum(self):
+        return False
+
+    def isSerializable(self):
+        return self.inner.isSerializable()
+
+    def tag(self):
+        return IDLType.Tags.sequence
+
+    def complete(self, scope):
+        self.inner = self.inner.complete(scope)
+        self.name = self.inner.name + "Sequence"
+        return self
+
+    def isDistinguishableFrom(self, other):
+        if other.isPromise():
+            return False
+        if other.isUnion():
+            # Just forward to the union; it'll deal
+            return other.isDistinguishableFrom(self)
+        return (other.isPrimitive() or other.isString() or other.isEnum() or
+                other.isDate() or other.isInterface() or
+                other.isDictionary() or
+                other.isCallback() or other.isMozMap())
+
+
+class IDLMozMapType(IDLParameterizedType):
+    def __init__(self, location, parameterType):
+        assert not parameterType.isVoid()
+
+        IDLParameterizedType.__init__(self, location, parameterType.name, parameterType)
+        # Need to set self.name up front if our inner type is already complete,
+        # since in that case our .complete() won't be called.
+        if self.inner.isComplete():
+            self.name = self.inner.name + "MozMap"
+
+    def __eq__(self, other):
+        return isinstance(other, IDLMozMapType) and self.inner == other.inner
+
+    def __str__(self):
+        return self.inner.__str__() + "MozMap"
+
+    def isMozMap(self):
+        return True
+
+    def tag(self):
+        return IDLType.Tags.mozmap
+
+    def complete(self, scope):
+        self.inner = self.inner.complete(scope)
+        self.name = self.inner.name + "MozMap"
+        return self
+
+    def unroll(self):
+        # We do not unroll our inner.  Just stop at ourselves.  That
+        # lets us add headers for both ourselves and our inner as
+        # needed.
+        return self
+
+    def isDistinguishableFrom(self, other):
+        if other.isPromise():
+            return False
+        if other.isUnion():
+            # Just forward to the union; it'll deal
+            return other.isDistinguishableFrom(self)
+        return (other.isPrimitive() or other.isString() or other.isEnum() or
+                other.isDate() or other.isNonCallbackInterface() or other.isSequence())
+
+    def isExposedInAllOf(self, exposureSet):
+        return self.inner.unroll().isExposedInAllOf(exposureSet)
+
+
+class IDLUnionType(IDLType):
+    def __init__(self, location, memberTypes):
+        IDLType.__init__(self, location, "")
+        self.memberTypes = memberTypes
+        self.hasNullableType = False
+        self._dictionaryType = None
+        self.flatMemberTypes = None
+        self.builtin = False
+
+    def __eq__(self, other):
+        return isinstance(other, IDLUnionType) and self.memberTypes == other.memberTypes
+
+    def __hash__(self):
+        assert self.isComplete()
+        return self.name.__hash__()
+
+    def isVoid(self):
+        return False
+
+    def isUnion(self):
+        return True
+
+    def isSerializable(self):
+        return all(m.isSerializable() for m in self.memberTypes)
+
+    def includesRestrictedFloat(self):
+        return any(t.includesRestrictedFloat() for t in self.memberTypes)
+
+    def tag(self):
+        return IDLType.Tags.union
+
+    def resolveType(self, parentScope):
+        assert isinstance(parentScope, IDLScope)
+        for t in self.memberTypes:
+            t.resolveType(parentScope)
+
+    def isComplete(self):
+        return self.flatMemberTypes is not None
+
+    def complete(self, scope):
+        def typeName(type):
+            if isinstance(type, IDLNullableType):
+                return typeName(type.inner) + "OrNull"
+            if isinstance(type, IDLWrapperType):
+                return typeName(type._identifier.object())
+            if isinstance(type, IDLObjectWithIdentifier):
+                return typeName(type.identifier)
+            return type.name
+
+        for (i, type) in enumerate(self.memberTypes):
+            if not type.isComplete():
+                self.memberTypes[i] = type.complete(scope)
+
+        self.name = "Or".join(typeName(type) for type in self.memberTypes)
+        self.flatMemberTypes = list(self.memberTypes)
+        i = 0
+        while i < len(self.flatMemberTypes):
+            if self.flatMemberTypes[i].nullable():
+                if self.hasNullableType:
+                    raise WebIDLError("Can't have more than one nullable types in a union",
+                                      [nullableType.location, self.flatMemberTypes[i].location])
+                if self.hasDictionaryType():
+                    raise WebIDLError("Can't have a nullable type and a "
+                                      "dictionary type in a union",
+                                      [self._dictionaryType.location,
+                                       self.flatMemberTypes[i].location])
+                self.hasNullableType = True
+                nullableType = self.flatMemberTypes[i]
+                self.flatMemberTypes[i] = self.flatMemberTypes[i].inner
+                continue
+            if self.flatMemberTypes[i].isDictionary():
+                if self.hasNullableType:
+                    raise WebIDLError("Can't have a nullable type and a "
+                                      "dictionary type in a union",
+                                      [nullableType.location,
+                                       self.flatMemberTypes[i].location])
+                self._dictionaryType = self.flatMemberTypes[i]
+            elif self.flatMemberTypes[i].isUnion():
+                self.flatMemberTypes[i:i + 1] = self.flatMemberTypes[i].memberTypes
+                continue
+            i += 1
+
+        for (i, t) in enumerate(self.flatMemberTypes[:-1]):
+            for u in self.flatMemberTypes[i + 1:]:
+                if not t.isDistinguishableFrom(u):
+                    raise WebIDLError("Flat member types of a union should be "
+                                      "distinguishable, " + str(t) + " is not "
+                                      "distinguishable from " + str(u),
+                                      [self.location, t.location, u.location])
+
+        return self
+
+    def isDistinguishableFrom(self, other):
+        if self.hasNullableType and other.nullable():
+            # Can't tell which type null should become
+            return False
+        if other.isUnion():
+            otherTypes = other.unroll().memberTypes
+        else:
+            otherTypes = [other]
+        # For every type in otherTypes, check that it's distinguishable from
+        # every type in our types
+        for u in otherTypes:
+            if any(not t.isDistinguishableFrom(u) for t in self.memberTypes):
+                return False
+        return True
+
+    def isExposedInAllOf(self, exposureSet):
+        # We could have different member types in different globals.  Just make sure that each thing in exposureSet has one of our member types exposed in it.
+        for globalName in exposureSet:
+            if not any(t.unroll().isExposedInAllOf(set([globalName])) for t
+                       in self.flatMemberTypes):
+                return False
+        return True
+
+    def hasDictionaryType(self):
+        return self._dictionaryType is not None
+
+    def hasPossiblyEmptyDictionaryType(self):
+        return (self._dictionaryType is not None and
+                self._dictionaryType.inner.canBeEmpty())
+
+    def _getDependentObjects(self):
+        return set(self.memberTypes)
+
+
+class IDLTypedefType(IDLType):
+    def __init__(self, location, innerType, name):
+        IDLType.__init__(self, location, name)
+        self.inner = innerType
+        self.builtin = False
+
+    def __eq__(self, other):
+        return isinstance(other, IDLTypedefType) and self.inner == other.inner
+
+    def __str__(self):
+        return self.name
+
+    def nullable(self):
+        return self.inner.nullable()
+
+    def isPrimitive(self):
+        return self.inner.isPrimitive()
+
+    def isBoolean(self):
+        return self.inner.isBoolean()
+
+    def isNumeric(self):
+        return self.inner.isNumeric()
+
+    def isString(self):
+        return self.inner.isString()
+
+    def isByteString(self):
+        return self.inner.isByteString()
+
+    def isDOMString(self):
+        return self.inner.isDOMString()
+
+    def isUSVString(self):
+        return self.inner.isUSVString()
+
+    def isVoid(self):
+        return self.inner.isVoid()
+
+    def isSequence(self):
+        return self.inner.isSequence()
+
+    def isMozMap(self):
+        return self.inner.isMozMap()
+
+    def isDictionary(self):
+        return self.inner.isDictionary()
+
+    def isArrayBuffer(self):
+        return self.inner.isArrayBuffer()
+
+    def isArrayBufferView(self):
+        return self.inner.isArrayBufferView()
+
+    def isSharedArrayBuffer(self):
+        return self.inner.isSharedArrayBuffer()
+
+    def isTypedArray(self):
+        return self.inner.isTypedArray()
+
+    def isInterface(self):
+        return self.inner.isInterface()
+
+    def isCallbackInterface(self):
+        return self.inner.isCallbackInterface()
+
+    def isNonCallbackInterface(self):
+        return self.inner.isNonCallbackInterface()
+
+    def isComplete(self):
+        return False
+
+    def complete(self, parentScope):
+        if not self.inner.isComplete():
+            self.inner = self.inner.complete(parentScope)
+        assert self.inner.isComplete()
+        return self.inner
+
+    # Do we need a resolveType impl?  I don't think it's particularly useful....
+
+    def tag(self):
+        return self.inner.tag()
+
+    def unroll(self):
+        return self.inner.unroll()
+
+    def isDistinguishableFrom(self, other):
+        return self.inner.isDistinguishableFrom(other)
+
+    def _getDependentObjects(self):
+        return self.inner._getDependentObjects()
+
+
+class IDLTypedef(IDLObjectWithIdentifier):
+    def __init__(self, location, parentScope, innerType, name):
+        identifier = IDLUnresolvedIdentifier(location, name)
+        IDLObjectWithIdentifier.__init__(self, location, parentScope, identifier)
+        self.innerType = innerType
+
+    def __str__(self):
+        return "Typedef %s %s" % (self.identifier.name, self.innerType)
+
+    def finish(self, parentScope):
+        if not self.innerType.isComplete():
+            self.innerType = self.innerType.complete(parentScope)
+
+    def validate(self):
+        pass
+
+    def isTypedef(self):
+        return True
+
+    def addExtendedAttributes(self, attrs):
+        assert len(attrs) == 0
+
+    def _getDependentObjects(self):
+        return self.innerType._getDependentObjects()
+
+
+class IDLWrapperType(IDLType):
+    def __init__(self, location, inner, promiseInnerType=None):
+        IDLType.__init__(self, location, inner.identifier.name)
+        self.inner = inner
+        self._identifier = inner.identifier
+        self.builtin = False
+        assert not promiseInnerType or inner.identifier.name == "Promise"
+        self._promiseInnerType = promiseInnerType
+
+    def __eq__(self, other):
+        return (isinstance(other, IDLWrapperType) and
+                self._identifier == other._identifier and
+                self.builtin == other.builtin)
+
+    def __str__(self):
+        return str(self.name) + " (Wrapper)"
+
+    def nullable(self):
+        return False
+
+    def isPrimitive(self):
+        return False
+
+    def isString(self):
+        return False
+
+    def isByteString(self):
+        return False
+
+    def isDOMString(self):
+        return False
+
+    def isUSVString(self):
+        return False
+
+    def isVoid(self):
+        return False
+
+    def isSequence(self):
+        return False
+
+    def isDictionary(self):
+        return isinstance(self.inner, IDLDictionary)
+
+    def isInterface(self):
+        return (isinstance(self.inner, IDLInterface) or
+                isinstance(self.inner, IDLExternalInterface))
+
+    def isCallbackInterface(self):
+        return self.isInterface() and self.inner.isCallback()
+
+    def isNonCallbackInterface(self):
+        return self.isInterface() and not self.inner.isCallback()
+
+    def isEnum(self):
+        return isinstance(self.inner, IDLEnum)
+
+    def isPromise(self):
+        return (isinstance(self.inner, IDLInterface) and
+                self.inner.identifier.name == "Promise")
+
+    def promiseInnerType(self):
+        assert self.isPromise()
+        return self._promiseInnerType
+
+    def isSerializable(self):
+        if self.isInterface():
+            if self.inner.isExternal():
+                return False
+            return any(m.isMethod() and m.isJsonifier() for m in self.inner.members)
+        elif self.isEnum():
+            return True
+        elif self.isDictionary():
+            return all(m.type.isSerializable() for m in self.inner.members)
+        else:
+            raise WebIDLError("IDLWrapperType wraps type %s that we don't know if "
+                              "is serializable" % type(self.inner), [self.location])
+
+    def resolveType(self, parentScope):
+        assert isinstance(parentScope, IDLScope)
+        self.inner.resolve(parentScope)
+
+    def isComplete(self):
+        return True
+
+    def tag(self):
+        if self.isInterface():
+            return IDLType.Tags.interface
+        elif self.isEnum():
+            return IDLType.Tags.enum
+        elif self.isDictionary():
+            return IDLType.Tags.dictionary
+        else:
+            assert False
+
+    def isDistinguishableFrom(self, other):
+        if self.isPromise():
+            return False
+        if other.isPromise():
+            return False
+        if other.isUnion():
+            # Just forward to the union; it'll deal
+            return other.isDistinguishableFrom(self)
+        assert self.isInterface() or self.isEnum() or self.isDictionary()
+        if self.isEnum():
+            return (other.isPrimitive() or other.isInterface() or other.isObject() or
+                    other.isCallback() or other.isDictionary() or
+                    other.isSequence() or other.isMozMap() or other.isDate())
+        if self.isDictionary() and other.nullable():
+            return False
+        if (other.isPrimitive() or other.isString() or other.isEnum() or
+            other.isDate() or other.isSequence()):
+            return True
+        if self.isDictionary():
+            return other.isNonCallbackInterface()
+
+        assert self.isInterface()
+        if other.isInterface():
+            if other.isSpiderMonkeyInterface():
+                # Just let |other| handle things
+                return other.isDistinguishableFrom(self)
+            assert self.isGeckoInterface() and other.isGeckoInterface()
+            if self.inner.isExternal() or other.unroll().inner.isExternal():
+                return self != other
+            return (len(self.inner.interfacesBasedOnSelf &
+                        other.unroll().inner.interfacesBasedOnSelf) == 0 and
+                    (self.isNonCallbackInterface() or
+                     other.isNonCallbackInterface()))
+        if (other.isDictionary() or other.isCallback() or
+            other.isMozMap()):
+            return self.isNonCallbackInterface()
+
+        # Not much else |other| can be
+        assert other.isObject()
+        return False
+
+    def isExposedInAllOf(self, exposureSet):
+        if not self.isInterface():
+            return True
+        iface = self.inner
+        if iface.isExternal():
+            # Let's say true, though ideally we'd only do this when
+            # exposureSet contains the primary global's name.
+            return True
+        if (self.isPromise() and
+            # Check the internal type
+            not self.promiseInnerType().unroll().isExposedInAllOf(exposureSet)):
+            return False
+        return iface.exposureSet.issuperset(exposureSet)
+
+    def _getDependentObjects(self):
+        # NB: The codegen for an interface type depends on
+        #  a) That the identifier is in fact an interface (as opposed to
+        #     a dictionary or something else).
+        #  b) The native type of the interface.
+        #  If we depend on the interface object we will also depend on
+        #  anything the interface depends on which is undesirable.  We
+        #  considered implementing a dependency just on the interface type
+        #  file, but then every modification to an interface would cause this
+        #  to be regenerated which is still undesirable.  We decided not to
+        #  depend on anything, reasoning that:
+        #  1) Changing the concrete type of the interface requires modifying
+        #     Bindings.conf, which is still a global dependency.
+        #  2) Changing an interface to a dictionary (or vice versa) with the
+        #     same identifier should be incredibly rare.
+        #
+        # On the other hand, if our type is a dictionary, we should
+        # depend on it, because the member types of a dictionary
+        # affect whether a method taking the dictionary as an argument
+        # takes a JSContext* argument or not.
+        if self.isDictionary():
+            return set([self.inner])
+        return set()
+
+
+class IDLBuiltinType(IDLType):
+
+    Types = enum(
+        # The integer types
+        'byte',
+        'octet',
+        'short',
+        'unsigned_short',
+        'long',
+        'unsigned_long',
+        'long_long',
+        'unsigned_long_long',
+        # Additional primitive types
+        'boolean',
+        'unrestricted_float',
+        'float',
+        'unrestricted_double',
+        # IMPORTANT: "double" must be the last primitive type listed
+        'double',
+        # Other types
+        'any',
+        'domstring',
+        'bytestring',
+        'usvstring',
+        'object',
+        'date',
+        'void',
+        # Funny stuff
+        'ArrayBuffer',
+        'ArrayBufferView',
+        'SharedArrayBuffer',
+        'Int8Array',
+        'Uint8Array',
+        'Uint8ClampedArray',
+        'Int16Array',
+        'Uint16Array',
+        'Int32Array',
+        'Uint32Array',
+        'Float32Array',
+        'Float64Array'
+        )
+
+    TagLookup = {
+        Types.byte: IDLType.Tags.int8,
+        Types.octet: IDLType.Tags.uint8,
+        Types.short: IDLType.Tags.int16,
+        Types.unsigned_short: IDLType.Tags.uint16,
+        Types.long: IDLType.Tags.int32,
+        Types.unsigned_long: IDLType.Tags.uint32,
+        Types.long_long: IDLType.Tags.int64,
+        Types.unsigned_long_long: IDLType.Tags.uint64,
+        Types.boolean: IDLType.Tags.bool,
+        Types.unrestricted_float: IDLType.Tags.unrestricted_float,
+        Types.float: IDLType.Tags.float,
+        Types.unrestricted_double: IDLType.Tags.unrestricted_double,
+        Types.double: IDLType.Tags.double,
+        Types.any: IDLType.Tags.any,
+        Types.domstring: IDLType.Tags.domstring,
+        Types.bytestring: IDLType.Tags.bytestring,
+        Types.usvstring: IDLType.Tags.usvstring,
+        Types.object: IDLType.Tags.object,
+        Types.date: IDLType.Tags.date,
+        Types.void: IDLType.Tags.void,
+        Types.ArrayBuffer: IDLType.Tags.interface,
+        Types.ArrayBufferView: IDLType.Tags.interface,
+        Types.SharedArrayBuffer: IDLType.Tags.interface,
+        Types.Int8Array: IDLType.Tags.interface,
+        Types.Uint8Array: IDLType.Tags.interface,
+        Types.Uint8ClampedArray: IDLType.Tags.interface,
+        Types.Int16Array: IDLType.Tags.interface,
+        Types.Uint16Array: IDLType.Tags.interface,
+        Types.Int32Array: IDLType.Tags.interface,
+        Types.Uint32Array: IDLType.Tags.interface,
+        Types.Float32Array: IDLType.Tags.interface,
+        Types.Float64Array: IDLType.Tags.interface
+    }
+
+    def __init__(self, location, name, type):
+        IDLType.__init__(self, location, name)
+        self.builtin = True
+        self._typeTag = type
+
+    def isPrimitive(self):
+        return self._typeTag <= IDLBuiltinType.Types.double
+
+    def isBoolean(self):
+        return self._typeTag == IDLBuiltinType.Types.boolean
+
+    def isNumeric(self):
+        return self.isPrimitive() and not self.isBoolean()
+
+    def isString(self):
+        return (self._typeTag == IDLBuiltinType.Types.domstring or
+                self._typeTag == IDLBuiltinType.Types.bytestring or
+                self._typeTag == IDLBuiltinType.Types.usvstring)
+
+    def isByteString(self):
+        return self._typeTag == IDLBuiltinType.Types.bytestring
+
+    def isDOMString(self):
+        return self._typeTag == IDLBuiltinType.Types.domstring
+
+    def isUSVString(self):
+        return self._typeTag == IDLBuiltinType.Types.usvstring
+
+    def isInteger(self):
+        return self._typeTag <= IDLBuiltinType.Types.unsigned_long_long
+
+    def isArrayBuffer(self):
+        return self._typeTag == IDLBuiltinType.Types.ArrayBuffer
+
+    def isArrayBufferView(self):
+        return self._typeTag == IDLBuiltinType.Types.ArrayBufferView
+
+    def isSharedArrayBuffer(self):
+        return self._typeTag == IDLBuiltinType.Types.SharedArrayBuffer
+
+    def isTypedArray(self):
+        return (self._typeTag >= IDLBuiltinType.Types.Int8Array and
+                self._typeTag <= IDLBuiltinType.Types.Float64Array)
+
+    def isInterface(self):
+        # TypedArray things are interface types per the TypedArray spec,
+        # but we handle them as builtins because SpiderMonkey implements
+        # all of it internally.
+        return (self.isArrayBuffer() or
+                self.isArrayBufferView() or
+                self.isSharedArrayBuffer() or
+                self.isTypedArray())
+
+    def isNonCallbackInterface(self):
+        # All the interfaces we can be are non-callback
+        return self.isInterface()
+
+    def isFloat(self):
+        return (self._typeTag == IDLBuiltinType.Types.float or
+                self._typeTag == IDLBuiltinType.Types.double or
+                self._typeTag == IDLBuiltinType.Types.unrestricted_float or
+                self._typeTag == IDLBuiltinType.Types.unrestricted_double)
+
+    def isUnrestricted(self):
+        assert self.isFloat()
+        return (self._typeTag == IDLBuiltinType.Types.unrestricted_float or
+                self._typeTag == IDLBuiltinType.Types.unrestricted_double)
+
+    def isSerializable(self):
+        return self.isPrimitive() or self.isString() or self.isDate()
+
+    def includesRestrictedFloat(self):
+        return self.isFloat() and not self.isUnrestricted()
+
+    def tag(self):
+        return IDLBuiltinType.TagLookup[self._typeTag]
+
+    def isDistinguishableFrom(self, other):
+        if other.isPromise():
+            return False
+        if other.isUnion():
+            # Just forward to the union; it'll deal
+            return other.isDistinguishableFrom(self)
+        if self.isBoolean():
+            return (other.isNumeric() or other.isString() or other.isEnum() or
+                    other.isInterface() or other.isObject() or
+                    other.isCallback() or other.isDictionary() or
+                    other.isSequence() or other.isMozMap() or other.isDate())
+        if self.isNumeric():
+            return (other.isBoolean() or other.isString() or other.isEnum() or
+                    other.isInterface() or other.isObject() or
+                    other.isCallback() or other.isDictionary() or
+                    other.isSequence() or other.isMozMap() or other.isDate())
+        if self.isString():
+            return (other.isPrimitive() or other.isInterface() or
+                    other.isObject() or
+                    other.isCallback() or other.isDictionary() or
+                    other.isSequence() or other.isMozMap() or other.isDate())
+        if self.isAny():
+            # Can't tell "any" apart from anything
+            return False
+        if self.isObject():
+            return other.isPrimitive() or other.isString() or other.isEnum()
+        if self.isDate():
+            return (other.isPrimitive() or other.isString() or other.isEnum() or
+                    other.isInterface() or other.isCallback() or
+                    other.isDictionary() or other.isSequence() or
+                    other.isMozMap())
+        if self.isVoid():
+            return not other.isVoid()
+        # Not much else we could be!
+        assert self.isSpiderMonkeyInterface()
+        # Like interfaces, but we know we're not a callback
+        return (other.isPrimitive() or other.isString() or other.isEnum() or
+                other.isCallback() or other.isDictionary() or
+                other.isSequence() or other.isMozMap() or other.isDate() or
+                (other.isInterface() and (
+                 # ArrayBuffer is distinguishable from everything
+                 # that's not an ArrayBuffer or a callback interface
+                 (self.isArrayBuffer() and not other.isArrayBuffer()) or
+                 (self.isSharedArrayBuffer() and not other.isSharedArrayBuffer()) or
+                 # ArrayBufferView is distinguishable from everything
+                 # that's not an ArrayBufferView or typed array.
+                 (self.isArrayBufferView() and not other.isArrayBufferView() and
+                  not other.isTypedArray()) or
+                 # Typed arrays are distinguishable from everything
+                 # except ArrayBufferView and the same type of typed
+                 # array
+                 (self.isTypedArray() and not other.isArrayBufferView() and not
+                  (other.isTypedArray() and other.name == self.name)))))
+
+    def _getDependentObjects(self):
+        return set()
+
+BuiltinTypes = {
+    IDLBuiltinType.Types.byte:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Byte",
+                       IDLBuiltinType.Types.byte),
+    IDLBuiltinType.Types.octet:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Octet",
+                       IDLBuiltinType.Types.octet),
+    IDLBuiltinType.Types.short:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Short",
+                       IDLBuiltinType.Types.short),
+    IDLBuiltinType.Types.unsigned_short:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "UnsignedShort",
+                       IDLBuiltinType.Types.unsigned_short),
+    IDLBuiltinType.Types.long:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Long",
+                       IDLBuiltinType.Types.long),
+    IDLBuiltinType.Types.unsigned_long:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "UnsignedLong",
+                       IDLBuiltinType.Types.unsigned_long),
+    IDLBuiltinType.Types.long_long:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "LongLong",
+                       IDLBuiltinType.Types.long_long),
+    IDLBuiltinType.Types.unsigned_long_long:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "UnsignedLongLong",
+                       IDLBuiltinType.Types.unsigned_long_long),
+    IDLBuiltinType.Types.boolean:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Boolean",
+                       IDLBuiltinType.Types.boolean),
+    IDLBuiltinType.Types.float:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Float",
+                       IDLBuiltinType.Types.float),
+    IDLBuiltinType.Types.unrestricted_float:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "UnrestrictedFloat",
+                       IDLBuiltinType.Types.unrestricted_float),
+    IDLBuiltinType.Types.double:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Double",
+                       IDLBuiltinType.Types.double),
+    IDLBuiltinType.Types.unrestricted_double:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "UnrestrictedDouble",
+                       IDLBuiltinType.Types.unrestricted_double),
+    IDLBuiltinType.Types.any:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Any",
+                       IDLBuiltinType.Types.any),
+    IDLBuiltinType.Types.domstring:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "String",
+                       IDLBuiltinType.Types.domstring),
+    IDLBuiltinType.Types.bytestring:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "ByteString",
+                       IDLBuiltinType.Types.bytestring),
+    IDLBuiltinType.Types.usvstring:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "USVString",
+                       IDLBuiltinType.Types.usvstring),
+    IDLBuiltinType.Types.object:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Object",
+                       IDLBuiltinType.Types.object),
+    IDLBuiltinType.Types.date:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Date",
+                       IDLBuiltinType.Types.date),
+    IDLBuiltinType.Types.void:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Void",
+                       IDLBuiltinType.Types.void),
+    IDLBuiltinType.Types.ArrayBuffer:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "ArrayBuffer",
+                       IDLBuiltinType.Types.ArrayBuffer),
+    IDLBuiltinType.Types.ArrayBufferView:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "ArrayBufferView",
+                       IDLBuiltinType.Types.ArrayBufferView),
+    IDLBuiltinType.Types.SharedArrayBuffer:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "SharedArrayBuffer",
+                       IDLBuiltinType.Types.SharedArrayBuffer),
+    IDLBuiltinType.Types.Int8Array:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Int8Array",
+                       IDLBuiltinType.Types.Int8Array),
+    IDLBuiltinType.Types.Uint8Array:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Uint8Array",
+                       IDLBuiltinType.Types.Uint8Array),
+    IDLBuiltinType.Types.Uint8ClampedArray:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Uint8ClampedArray",
+                       IDLBuiltinType.Types.Uint8ClampedArray),
+    IDLBuiltinType.Types.Int16Array:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Int16Array",
+                       IDLBuiltinType.Types.Int16Array),
+    IDLBuiltinType.Types.Uint16Array:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Uint16Array",
+                       IDLBuiltinType.Types.Uint16Array),
+    IDLBuiltinType.Types.Int32Array:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Int32Array",
+                       IDLBuiltinType.Types.Int32Array),
+    IDLBuiltinType.Types.Uint32Array:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Uint32Array",
+                       IDLBuiltinType.Types.Uint32Array),
+    IDLBuiltinType.Types.Float32Array:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Float32Array",
+                       IDLBuiltinType.Types.Float32Array),
+    IDLBuiltinType.Types.Float64Array:
+        IDLBuiltinType(BuiltinLocation("<builtin type>"), "Float64Array",
+                       IDLBuiltinType.Types.Float64Array)
+}
+
+
+integerTypeSizes = {
+    IDLBuiltinType.Types.byte: (-128, 127),
+    IDLBuiltinType.Types.octet:  (0, 255),
+    IDLBuiltinType.Types.short: (-32768, 32767),
+    IDLBuiltinType.Types.unsigned_short: (0, 65535),
+    IDLBuiltinType.Types.long: (-2147483648, 2147483647),
+    IDLBuiltinType.Types.unsigned_long: (0, 4294967295),
+    IDLBuiltinType.Types.long_long: (-9223372036854775808, 9223372036854775807),
+    IDLBuiltinType.Types.unsigned_long_long: (0, 18446744073709551615)
+}
+
+
+def matchIntegerValueToType(value):
+    for type, extremes in integerTypeSizes.items():
+        (min, max) = extremes
+        if value <= max and value >= min:
+            return BuiltinTypes[type]
+
+    return None
+
+class NoCoercionFoundError(WebIDLError):
+    """
+    A class we use to indicate generic coercion failures because none of the
+    types worked out in IDLValue.coerceToType.
+    """
+
+class IDLValue(IDLObject):
+    def __init__(self, location, type, value):
+        IDLObject.__init__(self, location)
+        self.type = type
+        assert isinstance(type, IDLType)
+
+        self.value = value
+
+    def coerceToType(self, type, location):
+        if type == self.type:
+            return self  # Nothing to do
+
+        # We first check for unions to ensure that even if the union is nullable
+        # we end up with the right flat member type, not the union's type.
+        if type.isUnion():
+            # We use the flat member types here, because if we have a nullable
+            # member type, or a nested union, we want the type the value
+            # actually coerces to, not the nullable or nested union type.
+            for subtype in type.unroll().flatMemberTypes:
+                try:
+                    coercedValue = self.coerceToType(subtype, location)
+                    # Create a new IDLValue to make sure that we have the
+                    # correct float/double type.  This is necessary because we
+                    # use the value's type when it is a default value of a
+                    # union, and the union cares about the exact float type.
+                    return IDLValue(self.location, subtype, coercedValue.value)
+                except Exception as e:
+                    # Make sure to propagate out WebIDLErrors that are not the
+                    # generic "hey, we could not coerce to this type at all"
+                    # exception, because those are specific "coercion failed for
+                    # reason X" exceptions.  Note that we want to swallow
+                    # non-WebIDLErrors here, because those can just happen if
+                    # "type" is not something that can have a default value at
+                    # all.
+                    if (isinstance(e, WebIDLError) and
+                        not isinstance(e, NoCoercionFoundError)):
+                        raise e
+
+        # If the type allows null, rerun this matching on the inner type, except
+        # nullable enums.  We handle those specially, because we want our
+        # default string values to stay strings even when assigned to a nullable
+        # enum.
+        elif type.nullable() and not type.isEnum():
+            innerValue = self.coerceToType(type.inner, location)
+            return IDLValue(self.location, type, innerValue.value)
+
+        elif self.type.isInteger() and type.isInteger():
+            # We're both integer types.  See if we fit.
+
+            (min, max) = integerTypeSizes[type._typeTag]
+            if self.value <= max and self.value >= min:
+                # Promote
+                return IDLValue(self.location, type, self.value)
+            else:
+                raise WebIDLError("Value %s is out of range for type %s." %
+                                  (self.value, type), [location])
+        elif self.type.isInteger() and type.isFloat():
+            # Convert an integer literal into float
+            if -2**24 <= self.value <= 2**24:
+                return IDLValue(self.location, type, float(self.value))
+            else:
+                raise WebIDLError("Converting value %s to %s will lose precision." %
+                                  (self.value, type), [location])
+        elif self.type.isString() and type.isEnum():
+            # Just keep our string, but make sure it's a valid value for this enum
+            enum = type.unroll().inner
+            if self.value not in enum.values():
+                raise WebIDLError("'%s' is not a valid default value for enum %s"
+                                  % (self.value, enum.identifier.name),
+                                  [location, enum.location])
+            return self
+        elif self.type.isFloat() and type.isFloat():
+            if (not type.isUnrestricted() and
+                (self.value == float("inf") or self.value == float("-inf") or
+                 math.isnan(self.value))):
+                raise WebIDLError("Trying to convert unrestricted value %s to non-unrestricted"
+                                  % self.value, [location])
+            return IDLValue(self.location, type, self.value)
+        elif self.type.isString() and type.isUSVString():
+            # Allow USVStrings to use default value just like
+            # DOMString.  No coercion is required in this case as Codegen.py
+            # treats USVString just like DOMString, but with an
+            # extra normalization step.
+            assert self.type.isDOMString()
+            return self
+        elif self.type.isString() and type.isByteString():
+            # Allow ByteStrings to use a default value like DOMString.
+            # No coercion is required as Codegen.py will handle the
+            # extra steps. We want to make sure that our string contains
+            # only valid characters, so we check that here.
+            valid_ascii_lit = " " + string.ascii_letters + string.digits + string.punctuation
+            for idx, c in enumerate(self.value):
+                if c not in valid_ascii_lit:
+                    raise WebIDLError("Coercing this string literal %s to a ByteString is not supported yet. "
+                                      "Coercion failed due to an unsupported byte %d at index %d."
+                                      % (self.value.__repr__(), ord(c), idx), [location])
+
+            return IDLValue(self.location, type, self.value)
+
+        raise NoCoercionFoundError("Cannot coerce type %s to type %s." %
+                                   (self.type, type), [location])
+
+    def _getDependentObjects(self):
+        return set()
+
+
+class IDLNullValue(IDLObject):
+    def __init__(self, location):
+        IDLObject.__init__(self, location)
+        self.type = None
+        self.value = None
+
+    def coerceToType(self, type, location):
+        if (not isinstance(type, IDLNullableType) and
+            not (type.isUnion() and type.hasNullableType) and
+            not (type.isUnion() and type.hasDictionaryType()) and
+            not type.isDictionary() and
+            not type.isAny()):
+            raise WebIDLError("Cannot coerce null value to type %s." % type,
+                              [location])
+
+        nullValue = IDLNullValue(self.location)
+        if type.isUnion() and not type.nullable() and type.hasDictionaryType():
+            # We're actually a default value for the union's dictionary member.
+            # Use its type.
+            for t in type.flatMemberTypes:
+                if t.isDictionary():
+                    nullValue.type = t
+                    return nullValue
+        nullValue.type = type
+        return nullValue
+
+    def _getDependentObjects(self):
+        return set()
+
+
+class IDLEmptySequenceValue(IDLObject):
+    def __init__(self, location):
+        IDLObject.__init__(self, location)
+        self.type = None
+        self.value = None
+
+    def coerceToType(self, type, location):
+        if type.isUnion():
+            # We use the flat member types here, because if we have a nullable
+            # member type, or a nested union, we want the type the value
+            # actually coerces to, not the nullable or nested union type.
+            for subtype in type.unroll().flatMemberTypes:
+                try:
+                    return self.coerceToType(subtype, location)
+                except:
+                    pass
+
+        if not type.isSequence():
+            raise WebIDLError("Cannot coerce empty sequence value to type %s." % type,
+                              [location])
+
+        emptySequenceValue = IDLEmptySequenceValue(self.location)
+        emptySequenceValue.type = type
+        return emptySequenceValue
+
+    def _getDependentObjects(self):
+        return set()
+
+
+class IDLUndefinedValue(IDLObject):
+    def __init__(self, location):
+        IDLObject.__init__(self, location)
+        self.type = None
+        self.value = None
+
+    def coerceToType(self, type, location):
+        if not type.isAny():
+            raise WebIDLError("Cannot coerce undefined value to type %s." % type,
+                              [location])
+
+        undefinedValue = IDLUndefinedValue(self.location)
+        undefinedValue.type = type
+        return undefinedValue
+
+    def _getDependentObjects(self):
+        return set()
+
+
+class IDLInterfaceMember(IDLObjectWithIdentifier, IDLExposureMixins):
+
+    Tags = enum(
+        'Const',
+        'Attr',
+        'Method',
+        'MaplikeOrSetlike',
+        'Iterable'
+    )
+
+    Special = enum(
+        'Static',
+        'Stringifier'
+    )
+
+    AffectsValues = ("Nothing", "Everything")
+    DependsOnValues = ("Nothing", "DOMState", "DeviceState", "Everything")
+
+    def __init__(self, location, identifier, tag, extendedAttrDict=None):
+        IDLObjectWithIdentifier.__init__(self, location, None, identifier)
+        IDLExposureMixins.__init__(self, location)
+        self.tag = tag
+        if extendedAttrDict is None:
+            self._extendedAttrDict = {}
+        else:
+            self._extendedAttrDict = extendedAttrDict
+
+    def isMethod(self):
+        return self.tag == IDLInterfaceMember.Tags.Method
+
+    def isAttr(self):
+        return self.tag == IDLInterfaceMember.Tags.Attr
+
+    def isConst(self):
+        return self.tag == IDLInterfaceMember.Tags.Const
+
+    def isMaplikeOrSetlikeOrIterable(self):
+        return (self.tag == IDLInterfaceMember.Tags.MaplikeOrSetlike or
+                self.tag == IDLInterfaceMember.Tags.Iterable)
+
+    def isMaplikeOrSetlike(self):
+        return self.tag == IDLInterfaceMember.Tags.MaplikeOrSetlike
+
+    def addExtendedAttributes(self, attrs):
+        for attr in attrs:
+            self.handleExtendedAttribute(attr)
+            attrlist = attr.listValue()
+            self._extendedAttrDict[attr.identifier()] = attrlist if len(attrlist) else True
+
+    def handleExtendedAttribute(self, attr):
+        pass
+
+    def getExtendedAttribute(self, name):
+        return self._extendedAttrDict.get(name, None)
+
+    def finish(self, scope):
+        # We better be exposed _somewhere_.
+        if (len(self._exposureGlobalNames) == 0):
+            print self.identifier.name
+        assert len(self._exposureGlobalNames) != 0
+        IDLExposureMixins.finish(self, scope)
+
+    def validate(self):
+        if (self.getExtendedAttribute("Pref") and
+            self.exposureSet != set([self._globalScope.primaryGlobalName])):
+            raise WebIDLError("[Pref] used on an interface member that is not "
+                              "%s-only" % self._globalScope.primaryGlobalName,
+                              [self.location])
+
+        if self.isAttr() or self.isMethod():
+            if self.affects == "Everything" and self.dependsOn != "Everything":
+                raise WebIDLError("Interface member is flagged as affecting "
+                                  "everything but not depending on everything. "
+                                  "That seems rather unlikely.",
+                                  [self.location])
+
+        if self.getExtendedAttribute("NewObject"):
+            if self.dependsOn == "Nothing" or self.dependsOn == "DOMState":
+                raise WebIDLError("A [NewObject] method is not idempotent, "
+                                  "so it has to depend on something other than DOM state.",
+                                  [self.location])
+            if (self.getExtendedAttribute("Cached") or
+                self.getExtendedAttribute("StoreInSlot")):
+                raise WebIDLError("A [NewObject] attribute shouldnt be "
+                                  "[Cached] or [StoreInSlot], since the point "
+                                  "of those is to keep returning the same "
+                                  "thing across multiple calls, which is not "
+                                  "what [NewObject] does.",
+                                  [self.location])
+
+    def _setDependsOn(self, dependsOn):
+        if self.dependsOn != "Everything":
+            raise WebIDLError("Trying to specify multiple different DependsOn, "
+                              "Pure, or Constant extended attributes for "
+                              "attribute", [self.location])
+        if dependsOn not in IDLInterfaceMember.DependsOnValues:
+            raise WebIDLError("Invalid [DependsOn=%s] on attribute" % dependsOn,
+                              [self.location])
+        self.dependsOn = dependsOn
+
+    def _setAffects(self, affects):
+        if self.affects != "Everything":
+            raise WebIDLError("Trying to specify multiple different Affects, "
+                              "Pure, or Constant extended attributes for "
+                              "attribute", [self.location])
+        if affects not in IDLInterfaceMember.AffectsValues:
+            raise WebIDLError("Invalid [Affects=%s] on attribute" % dependsOn,
+                              [self.location])
+        self.affects = affects
+
+    def _addAlias(self, alias):
+        if alias in self.aliases:
+            raise WebIDLError("Duplicate [Alias=%s] on attribute" % alias,
+                              [self.location])
+        self.aliases.append(alias)
+
+
+class IDLMaplikeOrSetlikeOrIterableBase(IDLInterfaceMember):
+
+    def __init__(self, location, identifier, ifaceType, keyType, valueType, ifaceKind):
+        IDLInterfaceMember.__init__(self, location, identifier, ifaceKind)
+        if keyType is not None:
+            assert isinstance(keyType, IDLType)
+        else:
+            assert valueType is not None
+        assert ifaceType in ['maplike', 'setlike', 'iterable']
+        if valueType is not None:
+            assert isinstance(valueType, IDLType)
+        self.keyType = keyType
+        self.valueType = valueType
+        self.maplikeOrSetlikeOrIterableType = ifaceType
+        self.disallowedMemberNames = []
+        self.disallowedNonMethodNames = []
+
+    def isMaplike(self):
+        return self.maplikeOrSetlikeOrIterableType == "maplike"
+
+    def isSetlike(self):
+        return self.maplikeOrSetlikeOrIterableType == "setlike"
+
+    def isIterable(self):
+        return self.maplikeOrSetlikeOrIterableType == "iterable"
+
+    def hasKeyType(self):
+        return self.keyType is not None
+
+    def hasValueType(self):
+        return self.valueType is not None
+
+    def checkCollisions(self, members, isAncestor):
+        for member in members:
+            # Check that there are no disallowed members
+            if (member.identifier.name in self.disallowedMemberNames and
+                not ((member.isMethod() and member.isMaplikeOrSetlikeOrIterableMethod()) or
+                     (member.isAttr() and member.isMaplikeOrSetlikeAttr()))):
+                raise WebIDLError("Member '%s' conflicts "
+                                  "with reserved %s name." %
+                                  (member.identifier.name,
+                                   self.maplikeOrSetlikeOrIterableType),
+                                  [self.location, member.location])
+            # Check that there are no disallowed non-method members.
+            # Ancestor members are always disallowed here; own members
+            # are disallowed only if they're non-methods.
+            if ((isAncestor or member.isAttr() or member.isConst()) and
+                member.identifier.name in self.disallowedNonMethodNames):
+                raise WebIDLError("Member '%s' conflicts "
+                                  "with reserved %s method." %
+                                  (member.identifier.name,
+                                   self.maplikeOrSetlikeOrIterableType),
+                                  [self.location, member.location])
+
+    def addMethod(self, name, members, allowExistingOperations, returnType, args=[],
+                  chromeOnly=False, isPure=False, affectsNothing=False, newObject=False,
+                  isIteratorAlias=False):
+        """
+        Create an IDLMethod based on the parameters passed in.
+
+        - members is the member list to add this function to, since this is
+          called during the member expansion portion of interface object
+          building.
+
+        - chromeOnly is only True for read-only js implemented classes, to
+        implement underscore prefixed convenience functions which would
+        otherwise not be available, unlike the case of C++ bindings.
+
+        - isPure is only True for idempotent functions, so it is not valid for
+        things like keys, values, etc. that return a new object every time.
+
+        - affectsNothing means that nothing changes due to this method, which
+          affects JIT optimization behavior
+
+        - newObject means the method creates and returns a new object.
+
+        """
+        # Only add name to lists for collision checks if it's not chrome
+        # only.
+        if chromeOnly:
+            name = "__" + name
+        else:
+            if not allowExistingOperations:
+                self.disallowedMemberNames.append(name)
+            else:
+                self.disallowedNonMethodNames.append(name)
+        # If allowExistingOperations is True, and another operation exists
+        # with the same name as the one we're trying to add, don't add the
+        # maplike/setlike operation. However, if the operation is static,
+        # then fail by way of creating the function, which will cause a
+        # naming conflict, per the spec.
+        if allowExistingOperations:
+            for m in members:
+                if m.identifier.name == name and m.isMethod() and not m.isStatic():
+                    return
+        method = IDLMethod(self.location,
+                           IDLUnresolvedIdentifier(self.location, name, allowDoubleUnderscore=chromeOnly),
+                           returnType, args, maplikeOrSetlikeOrIterable=self)
+        # We need to be able to throw from declaration methods
+        method.addExtendedAttributes(
+            [IDLExtendedAttribute(self.location, ("Throws",))])
+        if chromeOnly:
+            method.addExtendedAttributes(
+                [IDLExtendedAttribute(self.location, ("ChromeOnly",))])
+        if isPure:
+            method.addExtendedAttributes(
+                [IDLExtendedAttribute(self.location, ("Pure",))])
+        # Following attributes are used for keys/values/entries. Can't mark
+        # them pure, since they return a new object each time they are run.
+        if affectsNothing:
+            method.addExtendedAttributes(
+                [IDLExtendedAttribute(self.location, ("DependsOn", "Everything")),
+                 IDLExtendedAttribute(self.location, ("Affects", "Nothing"))])
+        if newObject:
+            method.addExtendedAttributes(
+                [IDLExtendedAttribute(self.location, ("NewObject",))])
+        if isIteratorAlias:
+            method.addExtendedAttributes(
+                [IDLExtendedAttribute(self.location, ("Alias", "@@iterator"))])
+        members.append(method)
+
+    def resolve(self, parentScope):
+        if self.keyType:
+            self.keyType.resolveType(parentScope)
+        if self.valueType:
+            self.valueType.resolveType(parentScope)
+
+    def finish(self, scope):
+        IDLInterfaceMember.finish(self, scope)
+        if self.keyType and not self.keyType.isComplete():
+            t = self.keyType.complete(scope)
+
+            assert not isinstance(t, IDLUnresolvedType)
+            assert not isinstance(t, IDLTypedefType)
+            assert not isinstance(t.name, IDLUnresolvedIdentifier)
+            self.keyType = t
+        if self.valueType and not self.valueType.isComplete():
+            t = self.valueType.complete(scope)
+
+            assert not isinstance(t, IDLUnresolvedType)
+            assert not isinstance(t, IDLTypedefType)
+            assert not isinstance(t.name, IDLUnresolvedIdentifier)
+            self.valueType = t
+
+    def validate(self):
+        IDLInterfaceMember.validate(self)
+
+    def handleExtendedAttribute(self, attr):
+        IDLInterfaceMember.handleExtendedAttribute(self, attr)
+
+    def _getDependentObjects(self):
+        deps = set()
+        if self.keyType:
+            deps.add(self.keyType)
+        if self.valueType:
+            deps.add(self.valueType)
+        return deps
+
+    def getForEachArguments(self):
+        return [IDLArgument(self.location,
+                            IDLUnresolvedIdentifier(BuiltinLocation("<auto-generated-identifier>"),
+                                                    "callback"),
+                            BuiltinTypes[IDLBuiltinType.Types.object]),
+                IDLArgument(self.location,
+                            IDLUnresolvedIdentifier(BuiltinLocation("<auto-generated-identifier>"),
+                                                    "thisArg"),
+                            BuiltinTypes[IDLBuiltinType.Types.any],
+                            optional=True)]
+
+# Iterable adds ES6 iterator style functions and traits
+# (keys/values/entries/@@iterator) to an interface.
+class IDLIterable(IDLMaplikeOrSetlikeOrIterableBase):
+
+    def __init__(self, location, identifier, keyType, valueType=None, scope=None):
+        IDLMaplikeOrSetlikeOrIterableBase.__init__(self, location, identifier,
+                                                   "iterable", keyType, valueType,
+                                                   IDLInterfaceMember.Tags.Iterable)
+        self.iteratorType = None
+
+    def __str__(self):
+        return "declared iterable with key '%s' and value '%s'" % (self.keyType, self.valueType)
+
+    def expand(self, members, isJSImplemented):
+        """
+        In order to take advantage of all of the method machinery in Codegen,
+        we generate our functions as if they were part of the interface
+        specification during parsing.
+        """
+        # We only need to add entries/keys/values here if we're a pair iterator.
+        # Value iterators just copy these from %ArrayPrototype% instead.
+        if not self.isPairIterator():
+            return
+
+        # object entries()
+        self.addMethod("entries", members, False, self.iteratorType,
+                       affectsNothing=True, newObject=True,
+                       isIteratorAlias=True)
+        # object keys()
+        self.addMethod("keys", members, False, self.iteratorType,
+                       affectsNothing=True, newObject=True)
+        # object values()
+        self.addMethod("values", members, False, self.iteratorType,
+                       affectsNothing=True, newObject=True)
+
+        # void forEach(callback(valueType, keyType), optional any thisArg)
+        self.addMethod("forEach", members, False,
+                       BuiltinTypes[IDLBuiltinType.Types.void],
+                       self.getForEachArguments())
+
+    def isValueIterator(self):
+        return not self.isPairIterator()
+
+    def isPairIterator(self):
+        return self.hasKeyType()
+
+# MaplikeOrSetlike adds ES6 map-or-set-like traits to an interface.
+class IDLMaplikeOrSetlike(IDLMaplikeOrSetlikeOrIterableBase):
+
+    def __init__(self, location, identifier, maplikeOrSetlikeType,
+                 readonly, keyType, valueType):
+        IDLMaplikeOrSetlikeOrIterableBase.__init__(self, location, identifier, maplikeOrSetlikeType,
+                                                   keyType, valueType, IDLInterfaceMember.Tags.MaplikeOrSetlike)
+        self.readonly = readonly
+        self.slotIndices = None
+
+        # When generating JSAPI access code, we need to know the backing object
+        # type prefix to create the correct function. Generate here for reuse.
+        if self.isMaplike():
+            self.prefix = 'Map'
+        elif self.isSetlike():
+            self.prefix = 'Set'
+
+    def __str__(self):
+        return "declared '%s' with key '%s'" % (self.maplikeOrSetlikeOrIterableType, self.keyType)
+
+    def expand(self, members, isJSImplemented):
+        """
+        In order to take advantage of all of the method machinery in Codegen,
+        we generate our functions as if they were part of the interface
+        specification during parsing.
+        """
+        # Both maplike and setlike have a size attribute
+        members.append(IDLAttribute(self.location,
+                                    IDLUnresolvedIdentifier(BuiltinLocation("<auto-generated-identifier>"), "size"),
+                                    BuiltinTypes[IDLBuiltinType.Types.unsigned_long],
+                                    True,
+                                    maplikeOrSetlike=self))
+        self.reserved_ro_names = ["size"]
+        self.disallowedMemberNames.append("size")
+
+        # object entries()
+        self.addMethod("entries", members, False, BuiltinTypes[IDLBuiltinType.Types.object],
+                       affectsNothing=True, isIteratorAlias=self.isMaplike())
+        # object keys()
+        self.addMethod("keys", members, False, BuiltinTypes[IDLBuiltinType.Types.object],
+                       affectsNothing=True)
+        # object values()
+        self.addMethod("values", members, False, BuiltinTypes[IDLBuiltinType.Types.object],
+                       affectsNothing=True, isIteratorAlias=self.isSetlike())
+
+        # void forEach(callback(valueType, keyType), thisVal)
+        self.addMethod("forEach", members, False, BuiltinTypes[IDLBuiltinType.Types.void],
+                       self.getForEachArguments())
+
+        def getKeyArg():
+            return IDLArgument(self.location,
+                               IDLUnresolvedIdentifier(self.location, "key"),
+                               self.keyType)
+
+        # boolean has(keyType key)
+        self.addMethod("has", members, False, BuiltinTypes[IDLBuiltinType.Types.boolean],
+                       [getKeyArg()], isPure=True)
+
+        if not self.readonly:
+            # void clear()
+            self.addMethod("clear", members, True, BuiltinTypes[IDLBuiltinType.Types.void],
+                           [])
+            # boolean delete(keyType key)
+            self.addMethod("delete", members, True,
+                           BuiltinTypes[IDLBuiltinType.Types.boolean], [getKeyArg()])
+
+        # Always generate underscored functions (e.g. __add, __clear) for js
+        # implemented interfaces as convenience functions.
+        if isJSImplemented:
+            # void clear()
+            self.addMethod("clear", members, True, BuiltinTypes[IDLBuiltinType.Types.void],
+                           [], chromeOnly=True)
+            # boolean delete(keyType key)
+            self.addMethod("delete", members, True,
+                           BuiltinTypes[IDLBuiltinType.Types.boolean], [getKeyArg()],
+                           chromeOnly=True)
+
+        if self.isSetlike():
+            if not self.readonly:
+                # Add returns the set object it just added to.
+                # object add(keyType key)
+
+                self.addMethod("add", members, True,
+                               BuiltinTypes[IDLBuiltinType.Types.object], [getKeyArg()])
+            if isJSImplemented:
+                self.addMethod("add", members, True,
+                               BuiltinTypes[IDLBuiltinType.Types.object], [getKeyArg()],
+                               chromeOnly=True)
+            return
+
+        # If we get this far, we're a maplike declaration.
+
+        # valueType get(keyType key)
+        #
+        # Note that instead of the value type, we're using any here. The
+        # validity checks should happen as things are inserted into the map,
+        # and using any as the return type makes code generation much simpler.
+        #
+        # TODO: Bug 1155340 may change this to use specific type to provide
+        # more info to JIT.
+        self.addMethod("get", members, False, BuiltinTypes[IDLBuiltinType.Types.any],
+                       [getKeyArg()], isPure=True)
+
+        def getValueArg():
+            return IDLArgument(self.location,
+                               IDLUnresolvedIdentifier(self.location, "value"),
+                               self.valueType)
+
+        if not self.readonly:
+            self.addMethod("set", members, True, BuiltinTypes[IDLBuiltinType.Types.object],
+                           [getKeyArg(), getValueArg()])
+        if isJSImplemented:
+            self.addMethod("set", members, True, BuiltinTypes[IDLBuiltinType.Types.object],
+                           [getKeyArg(), getValueArg()], chromeOnly=True)
+
+class IDLConst(IDLInterfaceMember):
+    def __init__(self, location, identifier, type, value):
+        IDLInterfaceMember.__init__(self, location, identifier,
+                                    IDLInterfaceMember.Tags.Const)
+
+        assert isinstance(type, IDLType)
+        if type.isDictionary():
+            raise WebIDLError("A constant cannot be of a dictionary type",
+                              [self.location])
+        self.type = type
+        self.value = value
+
+        if identifier.name == "prototype":
+            raise WebIDLError("The identifier of a constant must not be 'prototype'",
+                              [location])
+
+    def __str__(self):
+        return "'%s' const '%s'" % (self.type, self.identifier)
+
+    def finish(self, scope):
+        IDLInterfaceMember.finish(self, scope)
+
+        if not self.type.isComplete():
+            type = self.type.complete(scope)
+            if not type.isPrimitive() and not type.isString():
+                locations = [self.type.location, type.location]
+                try:
+                    locations.append(type.inner.location)
+                except:
+                    pass
+                raise WebIDLError("Incorrect type for constant", locations)
+            self.type = type
+
+        # The value might not match the type
+        coercedValue = self.value.coerceToType(self.type, self.location)
+        assert coercedValue
+
+        self.value = coercedValue
+
+    def validate(self):
+        IDLInterfaceMember.validate(self)
+
+    def handleExtendedAttribute(self, attr):
+        identifier = attr.identifier()
+        if identifier == "Exposed":
+            convertExposedAttrToGlobalNameSet(attr, self._exposureGlobalNames)
+        elif (identifier == "Pref" or
+              identifier == "ChromeOnly" or
+              identifier == "Func" or
+              identifier == "SecureContext"):
+            # Known attributes that we don't need to do anything with here
+            pass
+        else:
+            raise WebIDLError("Unknown extended attribute %s on constant" % identifier,
+                              [attr.location])
+        IDLInterfaceMember.handleExtendedAttribute(self, attr)
+
+    def _getDependentObjects(self):
+        return set([self.type, self.value])
+
+
+class IDLAttribute(IDLInterfaceMember):
+    def __init__(self, location, identifier, type, readonly, inherit=False,
+                 static=False, stringifier=False, maplikeOrSetlike=None,
+                 extendedAttrDict=None, navigatorObjectGetter=False):
+        IDLInterfaceMember.__init__(self, location, identifier,
+                                    IDLInterfaceMember.Tags.Attr,
+                                    extendedAttrDict=extendedAttrDict)
+
+        assert isinstance(type, IDLType)
+        self.type = type
+        self.readonly = readonly
+        self.inherit = inherit
+        self._static = static
+        self.lenientThis = False
+        self._unforgeable = False
+        self.stringifier = stringifier
+        self.enforceRange = False
+        self.clamp = False
+        self.slotIndices = None
+        assert maplikeOrSetlike is None or isinstance(maplikeOrSetlike, IDLMaplikeOrSetlike)
+        self.maplikeOrSetlike = maplikeOrSetlike
+        self.dependsOn = "Everything"
+        self.affects = "Everything"
+        self.navigatorObjectGetter = navigatorObjectGetter
+
+        if static and identifier.name == "prototype":
+            raise WebIDLError("The identifier of a static attribute must not be 'prototype'",
+                              [location])
+
+        if readonly and inherit:
+            raise WebIDLError("An attribute cannot be both 'readonly' and 'inherit'",
+                              [self.location])
+
+    def isStatic(self):
+        return self._static
+
+    def forceStatic(self):
+        self._static = True
+
+    def __str__(self):
+        return "'%s' attribute '%s'" % (self.type, self.identifier)
+
+    def finish(self, scope):
+        IDLInterfaceMember.finish(self, scope)
+
+        if not self.type.isComplete():
+            t = self.type.complete(scope)
+
+            assert not isinstance(t, IDLUnresolvedType)
+            assert not isinstance(t, IDLTypedefType)
+            assert not isinstance(t.name, IDLUnresolvedIdentifier)
+            self.type = t
+
+        if self.type.isDictionary() and not self.getExtendedAttribute("Cached"):
+            raise WebIDLError("An attribute cannot be of a dictionary type",
+                              [self.location])
+        if self.type.isSequence() and not self.getExtendedAttribute("Cached"):
+            raise WebIDLError("A non-cached attribute cannot be of a sequence "
+                              "type", [self.location])
+        if self.type.isMozMap() and not self.getExtendedAttribute("Cached"):
+            raise WebIDLError("A non-cached attribute cannot be of a MozMap "
+                              "type", [self.location])
+        if self.type.isUnion():
+            for f in self.type.unroll().flatMemberTypes:
+                if f.isDictionary():
+                    raise WebIDLError("An attribute cannot be of a union "
+                                      "type if one of its member types (or "
+                                      "one of its member types's member "
+                                      "types, and so on) is a dictionary "
+                                      "type", [self.location, f.location])
+                if f.isSequence():
+                    raise WebIDLError("An attribute cannot be of a union "
+                                      "type if one of its member types (or "
+                                      "one of its member types's member "
+                                      "types, and so on) is a sequence "
+                                      "type", [self.location, f.location])
+                if f.isMozMap():
+                    raise WebIDLError("An attribute cannot be of a union "
+                                      "type if one of its member types (or "
+                                      "one of its member types's member "
+                                      "types, and so on) is a MozMap "
+                                      "type", [self.location, f.location])
+        if not self.type.isInterface() and self.getExtendedAttribute("PutForwards"):
+            raise WebIDLError("An attribute with [PutForwards] must have an "
+                              "interface type as its type", [self.location])
+
+        if not self.type.isInterface() and self.getExtendedAttribute("SameObject"):
+            raise WebIDLError("An attribute with [SameObject] must have an "
+                              "interface type as its type", [self.location])
+
+    def validate(self):
+        def typeContainsChromeOnlyDictionaryMember(type):
+            if (type.nullable() or
+                type.isSequence() or
+                type.isMozMap()):
+                return typeContainsChromeOnlyDictionaryMember(type.inner)
+
+            if type.isUnion():
+                for memberType in type.flatMemberTypes:
+                    (contains, location) = typeContainsChromeOnlyDictionaryMember(memberType)
+                    if contains:
+                        return (True, location)
+
+            if type.isDictionary():
+                dictionary = type.inner
+                while dictionary:
+                    (contains, location) = dictionaryContainsChromeOnlyMember(dictionary)
+                    if contains:
+                        return (True, location)
+                    dictionary = dictionary.parent
+
+            return (False, None)
+
+        def dictionaryContainsChromeOnlyMember(dictionary):
+            for member in dictionary.members:
+                if member.getExtendedAttribute("ChromeOnly"):
+                    return (True, member.location)
+                (contains, location) = typeContainsChromeOnlyDictionaryMember(member.type)
+                if contains:
+                    return (True, location)
+            return (False, None)
+
+        IDLInterfaceMember.validate(self)
+
+        if (self.getExtendedAttribute("Cached") or
+            self.getExtendedAttribute("StoreInSlot")):
+            if not self.affects == "Nothing":
+                raise WebIDLError("Cached attributes and attributes stored in "
+                                  "slots must be Constant or Pure or "
+                                  "Affects=Nothing, since the getter won't always "
+                                  "be called.",
+                                  [self.location])
+            (contains, location) = typeContainsChromeOnlyDictionaryMember(self.type)
+            if contains:
+                raise WebIDLError("[Cached] and [StoreInSlot] must not be used "
+                                  "on an attribute whose type contains a "
+                                  "[ChromeOnly] dictionary member",
+                                  [self.location, location])
+        if self.getExtendedAttribute("Frozen"):
+            if (not self.type.isSequence() and not self.type.isDictionary() and
+                not self.type.isMozMap()):
+                raise WebIDLError("[Frozen] is only allowed on "
+                                  "sequence-valued, dictionary-valued, and "
+                                  "MozMap-valued attributes",
+                                  [self.location])
+        if not self.type.unroll().isExposedInAllOf(self.exposureSet):
+            raise WebIDLError("Attribute returns a type that is not exposed "
+                              "everywhere where the attribute is exposed",
+                              [self.location])
+
+    def handleExtendedAttribute(self, attr):
+        identifier = attr.identifier()
+        if identifier == "SetterThrows" and self.readonly:
+            raise WebIDLError("Readonly attributes must not be flagged as "
+                              "[SetterThrows]",
+                              [self.location])
+        elif (((identifier == "Throws" or identifier == "GetterThrows") and
+               self.getExtendedAttribute("StoreInSlot")) or
+              (identifier == "StoreInSlot" and
+               (self.getExtendedAttribute("Throws") or
+                self.getExtendedAttribute("GetterThrows")))):
+            raise WebIDLError("Throwing things can't be [StoreInSlot]",
+                              [attr.location])
+        elif identifier == "LenientThis":
+            if not attr.noArguments():
+                raise WebIDLError("[LenientThis] must take no arguments",
+                                  [attr.location])
+            if self.isStatic():
+                raise WebIDLError("[LenientThis] is only allowed on non-static "
+                                  "attributes", [attr.location, self.location])
+            if self.getExtendedAttribute("CrossOriginReadable"):
+                raise WebIDLError("[LenientThis] is not allowed in combination "
+                                  "with [CrossOriginReadable]",
+                                  [attr.location, self.location])
+            if self.getExtendedAttribute("CrossOriginWritable"):
+                raise WebIDLError("[LenientThis] is not allowed in combination "
+                                  "with [CrossOriginWritable]",
+                                  [attr.location, self.location])
+            self.lenientThis = True
+        elif identifier == "Unforgeable":
+            if self.isStatic():
+                raise WebIDLError("[Unforgeable] is only allowed on non-static "
+                                  "attributes", [attr.location, self.location])
+            self._unforgeable = True
+        elif identifier == "SameObject" and not self.readonly:
+            raise WebIDLError("[SameObject] only allowed on readonly attributes",
+                              [attr.location, self.location])
+        elif identifier == "Constant" and not self.readonly:
+            raise WebIDLError("[Constant] only allowed on readonly attributes",
+                              [attr.location, self.location])
+        elif identifier == "PutForwards":
+            if not self.readonly:
+                raise WebIDLError("[PutForwards] is only allowed on readonly "
+                                  "attributes", [attr.location, self.location])
+            if self.isStatic():
+                raise WebIDLError("[PutForwards] is only allowed on non-static "
+                                  "attributes", [attr.location, self.location])
+            if self.getExtendedAttribute("Replaceable") is not None:
+                raise WebIDLError("[PutForwards] and [Replaceable] can't both "
+                                  "appear on the same attribute",
+                                  [attr.location, self.location])
+            if not attr.hasValue():
+                raise WebIDLError("[PutForwards] takes an identifier",
+                                  [attr.location, self.location])
+        elif identifier == "Replaceable":
+            if not attr.noArguments():
+                raise WebIDLError("[Replaceable] must take no arguments",
+                                  [attr.location])
+            if not self.readonly:
+                raise WebIDLError("[Replaceable] is only allowed on readonly "
+                                  "attributes", [attr.location, self.location])
+            if self.isStatic():
+                raise WebIDLError("[Replaceable] is only allowed on non-static "
+                                  "attributes", [attr.location, self.location])
+            if self.getExtendedAttribute("PutForwards") is not None:
+                raise WebIDLError("[PutForwards] and [Replaceable] can't both "
+                                  "appear on the same attribute",
+                                  [attr.location, self.location])
+        elif identifier == "LenientSetter":
+            if not attr.noArguments():
+                raise WebIDLError("[LenientSetter] must take no arguments",
+                                  [attr.location])
+            if not self.readonly:
+                raise WebIDLError("[LenientSetter] is only allowed on readonly "
+                                  "attributes", [attr.location, self.location])
+            if self.isStatic():
+                raise WebIDLError("[LenientSetter] is only allowed on non-static "
+                                  "attributes", [attr.location, self.location])
+            if self.getExtendedAttribute("PutForwards") is not None:
+                raise WebIDLError("[LenientSetter] and [PutForwards] can't both "
+                                  "appear on the same attribute",
+                                  [attr.location, self.location])
+            if self.getExtendedAttribute("Replaceable") is not None:
+                raise WebIDLError("[LenientSetter] and [Replaceable] can't both "
+                                  "appear on the same attribute",
+                                  [attr.location, self.location])
+        elif identifier == "LenientFloat":
+            if self.readonly:
+                raise WebIDLError("[LenientFloat] used on a readonly attribute",
+                                  [attr.location, self.location])
+            if not self.type.includesRestrictedFloat():
+                raise WebIDLError("[LenientFloat] used on an attribute with a "
+                                  "non-restricted-float type",
+                                  [attr.location, self.location])
+        elif identifier == "EnforceRange":
+            if self.readonly:
+                raise WebIDLError("[EnforceRange] used on a readonly attribute",
+                                  [attr.location, self.location])
+            self.enforceRange = True
+        elif identifier == "Clamp":
+            if self.readonly:
+                raise WebIDLError("[Clamp] used on a readonly attribute",
+                                  [attr.location, self.location])
+            self.clamp = True
+        elif identifier == "StoreInSlot":
+            if self.getExtendedAttribute("Cached"):
+                raise WebIDLError("[StoreInSlot] and [Cached] must not be "
+                                  "specified on the same attribute",
+                                  [attr.location, self.location])
+        elif identifier == "Cached":
+            if self.getExtendedAttribute("StoreInSlot"):
+                raise WebIDLError("[Cached] and [StoreInSlot] must not be "
+                                  "specified on the same attribute",
+                                  [attr.location, self.location])
+        elif (identifier == "CrossOriginReadable" or
+              identifier == "CrossOriginWritable"):
+            if not attr.noArguments() and identifier == "CrossOriginReadable":
+                raise WebIDLError("[%s] must take no arguments" % identifier,
+                                  [attr.location])
+            if self.isStatic():
+                raise WebIDLError("[%s] is only allowed on non-static "
+                                  "attributes" % identifier,
+                                  [attr.location, self.location])
+            if self.getExtendedAttribute("LenientThis"):
+                raise WebIDLError("[LenientThis] is not allowed in combination "
+                                  "with [%s]" % identifier,
+                                  [attr.location, self.location])
+        elif identifier == "Exposed":
+            convertExposedAttrToGlobalNameSet(attr, self._exposureGlobalNames)
+        elif identifier == "Pure":
+            if not attr.noArguments():
+                raise WebIDLError("[Pure] must take no arguments",
+                                  [attr.location])
+            self._setDependsOn("DOMState")
+            self._setAffects("Nothing")
+        elif identifier == "Constant" or identifier == "SameObject":
+            if not attr.noArguments():
+                raise WebIDLError("[%s] must take no arguments" % identifier,
+                                  [attr.location])
+            self._setDependsOn("Nothing")
+            self._setAffects("Nothing")
+        elif identifier == "Affects":
+            if not attr.hasValue():
+                raise WebIDLError("[Affects] takes an identifier",
+                                  [attr.location])
+            self._setAffects(attr.value())
+        elif identifier == "DependsOn":
+            if not attr.hasValue():
+                raise WebIDLError("[DependsOn] takes an identifier",
+                                  [attr.location])
+            if (attr.value() != "Everything" and attr.value() != "DOMState" and
+                not self.readonly):
+                raise WebIDLError("[DependsOn=%s] only allowed on "
+                                  "readonly attributes" % attr.value(),
+                                  [attr.location, self.location])
+            self._setDependsOn(attr.value())
+        elif identifier == "UseCounter":
+            if self.stringifier:
+                raise WebIDLError("[UseCounter] must not be used on a "
+                                  "stringifier attribute",
+                                  [attr.location, self.location])
+        elif identifier == "Unscopable":
+            if not attr.noArguments():
+                raise WebIDLError("[Unscopable] must take no arguments",
+                                  [attr.location])
+            if self.isStatic():
+                raise WebIDLError("[Unscopable] is only allowed on non-static "
+                                  "attributes and operations",
+                                  [attr.location, self.location])
+        elif (identifier == "Pref" or
+              identifier == "Deprecated" or
+              identifier == "SetterThrows" or
+              identifier == "Throws" or
+              identifier == "GetterThrows" or
+              identifier == "ChromeOnly" or
+              identifier == "Func" or
+              identifier == "SecureContext" or
+              identifier == "Frozen" or
+              identifier == "NewObject" or
+              identifier == "UnsafeInPrerendering" or
+              identifier == "NeedsSubjectPrincipal" or
+              identifier == "NeedsCallerType" or
+              identifier == "ReturnValueNeedsContainsHack" or
+              identifier == "BinaryName"):
+            # Known attributes that we don't need to do anything with here
+            pass
+        else:
+            raise WebIDLError("Unknown extended attribute %s on attribute" % identifier,
+                              [attr.location])
+        IDLInterfaceMember.handleExtendedAttribute(self, attr)
+
+    def resolve(self, parentScope):
+        assert isinstance(parentScope, IDLScope)
+        self.type.resolveType(parentScope)
+        IDLObjectWithIdentifier.resolve(self, parentScope)
+
+    def addExtendedAttributes(self, attrs):
+        attrs = self.checkForStringHandlingExtendedAttributes(attrs)
+        IDLInterfaceMember.addExtendedAttributes(self, attrs)
+
+    def hasLenientThis(self):
+        return self.lenientThis
+
+    def isMaplikeOrSetlikeAttr(self):
+        """
+        True if this attribute was generated from an interface with
+        maplike/setlike (e.g. this is the size attribute for
+        maplike/setlike)
+        """
+        return self.maplikeOrSetlike is not None
+
+    def isUnforgeable(self):
+        return self._unforgeable
+
+    def _getDependentObjects(self):
+        return set([self.type])
+
+
+class IDLArgument(IDLObjectWithIdentifier):
+    def __init__(self, location, identifier, type, optional=False, defaultValue=None, variadic=False, dictionaryMember=False):
+        IDLObjectWithIdentifier.__init__(self, location, None, identifier)
+
+        assert isinstance(type, IDLType)
+        self.type = type
+
+        self.optional = optional
+        self.defaultValue = defaultValue
+        self.variadic = variadic
+        self.dictionaryMember = dictionaryMember
+        self._isComplete = False
+        self.enforceRange = False
+        self.clamp = False
+        self._allowTreatNonCallableAsNull = False
+        self._extendedAttrDict = {}
+
+        assert not variadic or optional
+        assert not variadic or not defaultValue
+
+    def addExtendedAttributes(self, attrs):
+        attrs = self.checkForStringHandlingExtendedAttributes(
+            attrs,
+            isDictionaryMember=self.dictionaryMember,
+            isOptional=self.optional)
+        for attribute in attrs:
+            identifier = attribute.identifier()
+            if identifier == "Clamp":
+                if not attribute.noArguments():
+                    raise WebIDLError("[Clamp] must take no arguments",
+                                      [attribute.location])
+                if self.enforceRange:
+                    raise WebIDLError("[EnforceRange] and [Clamp] are mutually exclusive",
+                                      [self.location])
+                self.clamp = True
+            elif identifier == "EnforceRange":
+                if not attribute.noArguments():
+                    raise WebIDLError("[EnforceRange] must take no arguments",
+                                      [attribute.location])
+                if self.clamp:
+                    raise WebIDLError("[EnforceRange] and [Clamp] are mutually exclusive",
+                                      [self.location])
+                self.enforceRange = True
+            elif identifier == "TreatNonCallableAsNull":
+                self._allowTreatNonCallableAsNull = True
+            elif (self.dictionaryMember and
+                  (identifier == "ChromeOnly" or identifier == "Func")):
+                if not self.optional:
+                    raise WebIDLError("[%s] must not be used on a required "
+                                      "dictionary member" % identifier,
+                                      [attribute.location])
+            else:
+                raise WebIDLError("Unhandled extended attribute on %s" %
+                                  ("a dictionary member" if self.dictionaryMember else
+                                   "an argument"),
+                                  [attribute.location])
+            attrlist = attribute.listValue()
+            self._extendedAttrDict[identifier] = attrlist if len(attrlist) else True
+
+    def getExtendedAttribute(self, name):
+        return self._extendedAttrDict.get(name, None)
+
+    def isComplete(self):
+        return self._isComplete
+
+    def complete(self, scope):
+        if self._isComplete:
+            return
+
+        self._isComplete = True
+
+        if not self.type.isComplete():
+            type = self.type.complete(scope)
+            assert not isinstance(type, IDLUnresolvedType)
+            assert not isinstance(type, IDLTypedefType)
+            assert not isinstance(type.name, IDLUnresolvedIdentifier)
+            self.type = type
+
+        if ((self.type.isDictionary() or
+             self.type.isUnion() and self.type.unroll().hasDictionaryType()) and
+            self.optional and not self.defaultValue and not self.variadic):
+            # Default optional non-variadic dictionaries to null,
+            # for simplicity, so the codegen doesn't have to special-case this.
+            self.defaultValue = IDLNullValue(self.location)
+        elif self.type.isAny():
+            assert (self.defaultValue is None or
+                    isinstance(self.defaultValue, IDLNullValue))
+            # optional 'any' values always have a default value
+            if self.optional and not self.defaultValue and not self.variadic:
+                # Set the default value to undefined, for simplicity, so the
+                # codegen doesn't have to special-case this.
+                self.defaultValue = IDLUndefinedValue(self.location)
+
+        # Now do the coercing thing; this needs to happen after the
+        # above creation of a default value.
+        if self.defaultValue:
+            self.defaultValue = self.defaultValue.coerceToType(self.type,
+                                                               self.location)
+            assert self.defaultValue
+
+    def allowTreatNonCallableAsNull(self):
+        return self._allowTreatNonCallableAsNull
+
+    def _getDependentObjects(self):
+        deps = set([self.type])
+        if self.defaultValue:
+            deps.add(self.defaultValue)
+        return deps
+
+    def canHaveMissingValue(self):
+        return self.optional and not self.defaultValue
+
+
+class IDLCallback(IDLObjectWithScope):
+    def __init__(self, location, parentScope, identifier, returnType, arguments):
+        assert isinstance(returnType, IDLType)
+
+        self._returnType = returnType
+        # Clone the list
+        self._arguments = list(arguments)
+
+        IDLObjectWithScope.__init__(self, location, parentScope, identifier)
+
+        for (returnType, arguments) in self.signatures():
+            for argument in arguments:
+                argument.resolve(self)
+
+        self._treatNonCallableAsNull = False
+        self._treatNonObjectAsNull = False
+
+    def isCallback(self):
+        return True
+
+    def signatures(self):
+        return [(self._returnType, self._arguments)]
+
+    def finish(self, scope):
+        if not self._returnType.isComplete():
+            type = self._returnType.complete(scope)
+
+            assert not isinstance(type, IDLUnresolvedType)
+            assert not isinstance(type, IDLTypedefType)
+            assert not isinstance(type.name, IDLUnresolvedIdentifier)
+            self._returnType = type
+
+        for argument in self._arguments:
+            if argument.type.isComplete():
+                continue
+
+            type = argument.type.complete(scope)
+
+            assert not isinstance(type, IDLUnresolvedType)
+            assert not isinstance(type, IDLTypedefType)
+            assert not isinstance(type.name, IDLUnresolvedIdentifier)
+            argument.type = type
+
+    def validate(self):
+        pass
+
+    def addExtendedAttributes(self, attrs):
+        unhandledAttrs = []
+        for attr in attrs:
+            if attr.identifier() == "TreatNonCallableAsNull":
+                self._treatNonCallableAsNull = True
+            elif attr.identifier() == "TreatNonObjectAsNull":
+                self._treatNonObjectAsNull = True
+            else:
+                unhandledAttrs.append(attr)
+        if self._treatNonCallableAsNull and self._treatNonObjectAsNull:
+            raise WebIDLError("Cannot specify both [TreatNonCallableAsNull] "
+                              "and [TreatNonObjectAsNull]", [self.location])
+        if len(unhandledAttrs) != 0:
+            IDLType.addExtendedAttributes(self, unhandledAttrs)
+
+    def _getDependentObjects(self):
+        return set([self._returnType] + self._arguments)
+
+
+class IDLCallbackType(IDLType):
+    def __init__(self, location, callback):
+        IDLType.__init__(self, location, callback.identifier.name)
+        self.callback = callback
+
+    def isCallback(self):
+        return True
+
+    def tag(self):
+        return IDLType.Tags.callback
+
+    def isDistinguishableFrom(self, other):
+        if other.isPromise():
+            return False
+        if other.isUnion():
+            # Just forward to the union; it'll deal
+            return other.isDistinguishableFrom(self)
+        return (other.isPrimitive() or other.isString() or other.isEnum() or
+                other.isNonCallbackInterface() or other.isDate() or
+                other.isSequence())
+
+    def _getDependentObjects(self):
+        return self.callback._getDependentObjects()
+
+
+class IDLMethodOverload:
+    """
+    A class that represents a single overload of a WebIDL method.  This is not
+    quite the same as an element of the "effective overload set" in the spec,
+    because separate IDLMethodOverloads are not created based on arguments being
+    optional.  Rather, when multiple methods have the same name, there is an
+    IDLMethodOverload for each one, all hanging off an IDLMethod representing
+    the full set of overloads.
+    """
+    def __init__(self, returnType, arguments, location):
+        self.returnType = returnType
+        # Clone the list of arguments, just in case
+        self.arguments = list(arguments)
+        self.location = location
+
+    def _getDependentObjects(self):
+        deps = set(self.arguments)
+        deps.add(self.returnType)
+        return deps
+
+
+class IDLMethod(IDLInterfaceMember, IDLScope):
+
+    Special = enum(
+        'Getter',
+        'Setter',
+        'Creator',
+        'Deleter',
+        'LegacyCaller',
+        base=IDLInterfaceMember.Special
+    )
+
+    NamedOrIndexed = enum(
+        'Neither',
+        'Named',
+        'Indexed'
+    )
+
+    def __init__(self, location, identifier, returnType, arguments,
+                 static=False, getter=False, setter=False, creator=False,
+                 deleter=False, specialType=NamedOrIndexed.Neither,
+                 legacycaller=False, stringifier=False, jsonifier=False,
+                 maplikeOrSetlikeOrIterable=None):
+        # REVIEW: specialType is NamedOrIndexed -- wow, this is messed up.
+        IDLInterfaceMember.__init__(self, location, identifier,
+                                    IDLInterfaceMember.Tags.Method)
+
+        self._hasOverloads = False
+
+        assert isinstance(returnType, IDLType)
+
+        # self._overloads is a list of IDLMethodOverloads
+        self._overloads = [IDLMethodOverload(returnType, arguments, location)]
+
+        assert isinstance(static, bool)
+        self._static = static
+        assert isinstance(getter, bool)
+        self._getter = getter
+        assert isinstance(setter, bool)
+        self._setter = setter
+        assert isinstance(creator, bool)
+        self._creator = creator
+        assert isinstance(deleter, bool)
+        self._deleter = deleter
+        assert isinstance(legacycaller, bool)
+        self._legacycaller = legacycaller
+        assert isinstance(stringifier, bool)
+        self._stringifier = stringifier
+        assert isinstance(jsonifier, bool)
+        self._jsonifier = jsonifier
+        assert maplikeOrSetlikeOrIterable is None or isinstance(maplikeOrSetlikeOrIterable, IDLMaplikeOrSetlikeOrIterableBase)
+        self.maplikeOrSetlikeOrIterable = maplikeOrSetlikeOrIterable
+        self._specialType = specialType
+        self._unforgeable = False
+        self.dependsOn = "Everything"
+        self.affects = "Everything"
+        self.aliases = []
+
+        if static and identifier.name == "prototype":
+            raise WebIDLError("The identifier of a static operation must not be 'prototype'",
+                              [location])
+
+        self.assertSignatureConstraints()
+
+    def __str__(self):
+        return "Method '%s'" % self.identifier
+
+    def assertSignatureConstraints(self):
+        if self._getter or self._deleter:
+            assert len(self._overloads) == 1
+            overload = self._overloads[0]
+            arguments = overload.arguments
+            assert len(arguments) == 1
+            assert (arguments[0].type == BuiltinTypes[IDLBuiltinType.Types.domstring] or
+                    arguments[0].type == BuiltinTypes[IDLBuiltinType.Types.unsigned_long])
+            assert not arguments[0].optional and not arguments[0].variadic
+            assert not self._getter or not overload.returnType.isVoid()
+
+        if self._setter or self._creator:
+            assert len(self._overloads) == 1
+            arguments = self._overloads[0].arguments
+            assert len(arguments) == 2
+            assert (arguments[0].type == BuiltinTypes[IDLBuiltinType.Types.domstring] or
+                    arguments[0].type == BuiltinTypes[IDLBuiltinType.Types.unsigned_long])
+            assert not arguments[0].optional and not arguments[0].variadic
+            assert not arguments[1].optional and not arguments[1].variadic
+
+        if self._stringifier:
+            assert len(self._overloads) == 1
+            overload = self._overloads[0]
+            assert len(overload.arguments) == 0
+            assert overload.returnType == BuiltinTypes[IDLBuiltinType.Types.domstring]
+
+        if self._jsonifier:
+            assert len(self._overloads) == 1
+            overload = self._overloads[0]
+            assert len(overload.arguments) == 0
+            assert overload.returnType == BuiltinTypes[IDLBuiltinType.Types.object]
+
+    def isStatic(self):
+        return self._static
+
+    def forceStatic(self):
+        self._static = True
+
+    def isGetter(self):
+        return self._getter
+
+    def isSetter(self):
+        return self._setter
+
+    def isCreator(self):
+        return self._creator
+
+    def isDeleter(self):
+        return self._deleter
+
+    def isNamed(self):
+        assert (self._specialType == IDLMethod.NamedOrIndexed.Named or
+                self._specialType == IDLMethod.NamedOrIndexed.Indexed)
+        return self._specialType == IDLMethod.NamedOrIndexed.Named
+
+    def isIndexed(self):
+        assert (self._specialType == IDLMethod.NamedOrIndexed.Named or
+                self._specialType == IDLMethod.NamedOrIndexed.Indexed)
+        return self._specialType == IDLMethod.NamedOrIndexed.Indexed
+
+    def isLegacycaller(self):
+        return self._legacycaller
+
+    def isStringifier(self):
+        return self._stringifier
+
+    def isJsonifier(self):
+        return self._jsonifier
+
+    def isMaplikeOrSetlikeOrIterableMethod(self):
+        """
+        True if this method was generated as part of a
+        maplike/setlike/etc interface (e.g. has/get methods)
+        """
+        return self.maplikeOrSetlikeOrIterable is not None
+
+    def isSpecial(self):
+        return (self.isGetter() or
+                self.isSetter() or
+                self.isCreator() or
+                self.isDeleter() or
+                self.isLegacycaller() or
+                self.isStringifier() or
+                self.isJsonifier())
+
+    def hasOverloads(self):
+        return self._hasOverloads
+
+    def isIdentifierLess(self):
+        """
+        True if the method name started with __, and if the method is not a
+        maplike/setlike method. Interfaces with maplike/setlike will generate
+        methods starting with __ for chrome only backing object access in JS
+        implemented interfaces, so while these functions use what is considered
+        an non-identifier name, they actually DO have an identifier.
+        """
+        return (self.identifier.name[:2] == "__" and
+                not self.isMaplikeOrSetlikeOrIterableMethod())
+
+    def resolve(self, parentScope):
+        assert isinstance(parentScope, IDLScope)
+        IDLObjectWithIdentifier.resolve(self, parentScope)
+        IDLScope.__init__(self, self.location, parentScope, self.identifier)
+        for (returnType, arguments) in self.signatures():
+            for argument in arguments:
+                argument.resolve(self)
+
+    def addOverload(self, method):
+        assert len(method._overloads) == 1
+
+        if self._extendedAttrDict != method ._extendedAttrDict:
+            raise WebIDLError("Extended attributes differ on different "
+                              "overloads of %s" % method.identifier,
+                              [self.location, method.location])
+
+        self._overloads.extend(method._overloads)
+
+        self._hasOverloads = True
+
+        if self.isStatic() != method.isStatic():
+            raise WebIDLError("Overloaded identifier %s appears with different values of the 'static' attribute" % method.identifier,
+                              [method.location])
+
+        if self.isLegacycaller() != method.isLegacycaller():
+            raise WebIDLError("Overloaded identifier %s appears with different values of the 'legacycaller' attribute" % method.identifier,
+                              [method.location])
+
+        # Can't overload special things!
+        assert not self.isGetter()
+        assert not method.isGetter()
+        assert not self.isSetter()
+        assert not method.isSetter()
+        assert not self.isCreator()
+        assert not method.isCreator()
+        assert not self.isDeleter()
+        assert not method.isDeleter()
+        assert not self.isStringifier()
+        assert not method.isStringifier()
+        assert not self.isJsonifier()
+        assert not method.isJsonifier()
+
+        return self
+
+    def signatures(self):
+        return [(overload.returnType, overload.arguments) for overload in
+                self._overloads]
+
+    def finish(self, scope):
+        IDLInterfaceMember.finish(self, scope)
+
+        for overload in self._overloads:
+            returnType = overload.returnType
+            if not returnType.isComplete():
+                returnType = returnType.complete(scope)
+                assert not isinstance(returnType, IDLUnresolvedType)
+                assert not isinstance(returnType, IDLTypedefType)
+                assert not isinstance(returnType.name, IDLUnresolvedIdentifier)
+                overload.returnType = returnType
+
+            for argument in overload.arguments:
+                if not argument.isComplete():
+                    argument.complete(scope)
+                assert argument.type.isComplete()
+
+        # Now compute various information that will be used by the
+        # WebIDL overload resolution algorithm.
+        self.maxArgCount = max(len(s[1]) for s in self.signatures())
+        self.allowedArgCounts = [i for i in range(self.maxArgCount+1)
+                                 if len(self.signaturesForArgCount(i)) != 0]
+
+    def validate(self):
+        IDLInterfaceMember.validate(self)
+
+        # Make sure our overloads are properly distinguishable and don't have
+        # different argument types before the distinguishing args.
+        for argCount in self.allowedArgCounts:
+            possibleOverloads = self.overloadsForArgCount(argCount)
+            if len(possibleOverloads) == 1:
+                continue
+            distinguishingIndex = self.distinguishingIndexForArgCount(argCount)
+            for idx in range(distinguishingIndex):
+                firstSigType = possibleOverloads[0].arguments[idx].type
+                for overload in possibleOverloads[1:]:
+                    if overload.arguments[idx].type != firstSigType:
+                        raise WebIDLError(
+                            "Signatures for method '%s' with %d arguments have "
+                            "different types of arguments at index %d, which "
+                            "is before distinguishing index %d" %
+                            (self.identifier.name, argCount, idx,
+                             distinguishingIndex),
+                            [self.location, overload.location])
+
+        overloadWithPromiseReturnType = None
+        overloadWithoutPromiseReturnType = None
+        for overload in self._overloads:
+            returnType = overload.returnType
+            if not returnType.unroll().isExposedInAllOf(self.exposureSet):
+                raise WebIDLError("Overload returns a type that is not exposed "
+                                  "everywhere where the method is exposed",
+                                  [overload.location])
+
+            variadicArgument = None
+
+            arguments = overload.arguments
+            for (idx, argument) in enumerate(arguments):
+                assert argument.type.isComplete()
+
+                if ((argument.type.isDictionary() and
+                     argument.type.inner.canBeEmpty())or
+                    (argument.type.isUnion() and
+                     argument.type.unroll().hasPossiblyEmptyDictionaryType())):
+                    # Optional dictionaries and unions containing optional
+                    # dictionaries at the end of the list or followed by
+                    # optional arguments must be optional.
+                    if (not argument.optional and
+                        all(arg.optional for arg in arguments[idx+1:])):
+                        raise WebIDLError("Dictionary argument or union "
+                                          "argument containing a dictionary "
+                                          "not followed by a required argument "
+                                          "must be optional",
+                                          [argument.location])
+
+                    # An argument cannot be a Nullable Dictionary
+                    if argument.type.nullable():
+                        raise WebIDLError("An argument cannot be a nullable "
+                                          "dictionary or nullable union "
+                                          "containing a dictionary",
+                                          [argument.location])
+
+                # Only the last argument can be variadic
+                if variadicArgument:
+                    raise WebIDLError("Variadic argument is not last argument",
+                                      [variadicArgument.location])
+                if argument.variadic:
+                    variadicArgument = argument
+
+            if returnType.isPromise():
+                overloadWithPromiseReturnType = overload
+            else:
+                overloadWithoutPromiseReturnType = overload
+
+        # Make sure either all our overloads return Promises or none do
+        if overloadWithPromiseReturnType and overloadWithoutPromiseReturnType:
+            raise WebIDLError("We have overloads with both Promise and "
+                              "non-Promise return types",
+                              [overloadWithPromiseReturnType.location,
+                               overloadWithoutPromiseReturnType.location])
+
+        if overloadWithPromiseReturnType and self._legacycaller:
+            raise WebIDLError("May not have a Promise return type for a "
+                              "legacycaller.",
+                              [overloadWithPromiseReturnType.location])
+
+        if self.getExtendedAttribute("StaticClassOverride") and not \
+           (self.identifier.scope.isJSImplemented() and self.isStatic()):
+            raise WebIDLError("StaticClassOverride can be applied to static"
+                              " methods on JS-implemented classes only.",
+                              [self.location])
+
+    def overloadsForArgCount(self, argc):
+        return [overload for overload in self._overloads if
+                len(overload.arguments) == argc or
+                (len(overload.arguments) > argc and
+                 all(arg.optional for arg in overload.arguments[argc:])) or
+                (len(overload.arguments) < argc and
+                 len(overload.arguments) > 0 and
+                 overload.arguments[-1].variadic)]
+
+    def signaturesForArgCount(self, argc):
+        return [(overload.returnType, overload.arguments) for overload
+                in self.overloadsForArgCount(argc)]
+
+    def locationsForArgCount(self, argc):
+        return [overload.location for overload in self.overloadsForArgCount(argc)]
+
+    def distinguishingIndexForArgCount(self, argc):
+        def isValidDistinguishingIndex(idx, signatures):
+            for (firstSigIndex, (firstRetval, firstArgs)) in enumerate(signatures[:-1]):
+                for (secondRetval, secondArgs) in signatures[firstSigIndex+1:]:
+                    if idx < len(firstArgs):
+                        firstType = firstArgs[idx].type
+                    else:
+                        assert(firstArgs[-1].variadic)
+                        firstType = firstArgs[-1].type
+                    if idx < len(secondArgs):
+                        secondType = secondArgs[idx].type
+                    else:
+                        assert(secondArgs[-1].variadic)
+                        secondType = secondArgs[-1].type
+                    if not firstType.isDistinguishableFrom(secondType):
+                        return False
+            return True
+        signatures = self.signaturesForArgCount(argc)
+        for idx in range(argc):
+            if isValidDistinguishingIndex(idx, signatures):
+                return idx
+        # No valid distinguishing index.  Time to throw
+        locations = self.locationsForArgCount(argc)
+        raise WebIDLError("Signatures with %d arguments for method '%s' are not "
+                          "distinguishable" % (argc, self.identifier.name),
+                          locations)
+
+    def handleExtendedAttribute(self, attr):
+        identifier = attr.identifier()
+        if identifier == "GetterThrows":
+            raise WebIDLError("Methods must not be flagged as "
+                              "[GetterThrows]",
+                              [attr.location, self.location])
+        elif identifier == "SetterThrows":
+            raise WebIDLError("Methods must not be flagged as "
+                              "[SetterThrows]",
+                              [attr.location, self.location])
+        elif identifier == "Unforgeable":
+            if self.isStatic():
+                raise WebIDLError("[Unforgeable] is only allowed on non-static "
+                                  "methods", [attr.location, self.location])
+            self._unforgeable = True
+        elif identifier == "SameObject":
+            raise WebIDLError("Methods must not be flagged as [SameObject]",
+                              [attr.location, self.location])
+        elif identifier == "Constant":
+            raise WebIDLError("Methods must not be flagged as [Constant]",
+                              [attr.location, self.location])
+        elif identifier == "PutForwards":
+            raise WebIDLError("Only attributes support [PutForwards]",
+                              [attr.location, self.location])
+        elif identifier == "LenientSetter":
+            raise WebIDLError("Only attributes support [LenientSetter]",
+                              [attr.location, self.location])
+        elif identifier == "LenientFloat":
+            # This is called before we've done overload resolution
+            assert len(self.signatures()) == 1
+            sig = self.signatures()[0]
+            if not sig[0].isVoid():
+                raise WebIDLError("[LenientFloat] used on a non-void method",
+                                  [attr.location, self.location])
+            if not any(arg.type.includesRestrictedFloat() for arg in sig[1]):
+                raise WebIDLError("[LenientFloat] used on an operation with no "
+                                  "restricted float type arguments",
+                                  [attr.location, self.location])
+        elif identifier == "Exposed":
+            convertExposedAttrToGlobalNameSet(attr, self._exposureGlobalNames)
+        elif (identifier == "CrossOriginCallable" or
+              identifier == "WebGLHandlesContextLoss"):
+            # Known no-argument attributes.
+            if not attr.noArguments():
+                raise WebIDLError("[%s] must take no arguments" % identifier,
+                                  [attr.location])
+        elif identifier == "Pure":
+            if not attr.noArguments():
+                raise WebIDLError("[Pure] must take no arguments",
+                                  [attr.location])
+            self._setDependsOn("DOMState")
+            self._setAffects("Nothing")
+        elif identifier == "Affects":
+            if not attr.hasValue():
+                raise WebIDLError("[Affects] takes an identifier",
+                                  [attr.location])
+            self._setAffects(attr.value())
+        elif identifier == "DependsOn":
+            if not attr.hasValue():
+                raise WebIDLError("[DependsOn] takes an identifier",
+                                  [attr.location])
+            self._setDependsOn(attr.value())
+        elif identifier == "Alias":
+            if not attr.hasValue():
+                raise WebIDLError("[Alias] takes an identifier or string",
+                                  [attr.location])
+            self._addAlias(attr.value())
+        elif identifier == "UseCounter":
+            if self.isSpecial():
+                raise WebIDLError("[UseCounter] must not be used on a special "
+                                  "operation",
+                                  [attr.location, self.location])
+        elif identifier == "Unscopable":
+            if not attr.noArguments():
+                raise WebIDLError("[Unscopable] must take no arguments",
+                                  [attr.location])
+            if self.isStatic():
+                raise WebIDLError("[Unscopable] is only allowed on non-static "
+                                  "attributes and operations",
+                                  [attr.location, self.location])
+        elif (identifier == "Throws" or
+              identifier == "NewObject" or
+              identifier == "ChromeOnly" or
+              identifier == "UnsafeInPrerendering" or
+              identifier == "Pref" or
+              identifier == "Deprecated" or
+              identifier == "Func" or
+              identifier == "SecureContext" or
+              identifier == "BinaryName" or
+              identifier == "NeedsSubjectPrincipal" or
+              identifier == "NeedsCallerType" or
+              identifier == "StaticClassOverride"):
+            # Known attributes that we don't need to do anything with here
+            pass
+        else:
+            raise WebIDLError("Unknown extended attribute %s on method" % identifier,
+                              [attr.location])
+        IDLInterfaceMember.handleExtendedAttribute(self, attr)
+
+    def returnsPromise(self):
+        return self._overloads[0].returnType.isPromise()
+
+    def isUnforgeable(self):
+        return self._unforgeable
+
+    def _getDependentObjects(self):
+        deps = set()
+        for overload in self._overloads:
+            deps.update(overload._getDependentObjects())
+        return deps
+
+
+class IDLImplementsStatement(IDLObject):
+    def __init__(self, location, implementor, implementee):
+        IDLObject.__init__(self, location)
+        self.implementor = implementor
+        self.implementee = implementee
+        self._finished = False
+
+    def finish(self, scope):
+        if self._finished:
+            return
+        assert(isinstance(self.implementor, IDLIdentifierPlaceholder))
+        assert(isinstance(self.implementee, IDLIdentifierPlaceholder))
+        implementor = self.implementor.finish(scope)
+        implementee = self.implementee.finish(scope)
+        # NOTE: we depend on not setting self.implementor and
+        # self.implementee here to keep track of the original
+        # locations.
+        if not isinstance(implementor, IDLInterface):
+            raise WebIDLError("Left-hand side of 'implements' is not an "
+                              "interface",
+                              [self.implementor.location])
+        if implementor.isCallback():
+            raise WebIDLError("Left-hand side of 'implements' is a callback "
+                              "interface",
+                              [self.implementor.location])
+        if not isinstance(implementee, IDLInterface):
+            raise WebIDLError("Right-hand side of 'implements' is not an "
+                              "interface",
+                              [self.implementee.location])
+        if implementee.isCallback():
+            raise WebIDLError("Right-hand side of 'implements' is a callback "
+                              "interface",
+                              [self.implementee.location])
+        implementor.addImplementedInterface(implementee)
+        self.implementor = implementor
+        self.implementee = implementee
+
+    def validate(self):
+        pass
+
+    def addExtendedAttributes(self, attrs):
+        assert len(attrs) == 0
+
+
+class IDLExtendedAttribute(IDLObject):
+    """
+    A class to represent IDL extended attributes so we can give them locations
+    """
+    def __init__(self, location, tuple):
+        IDLObject.__init__(self, location)
+        self._tuple = tuple
+
+    def identifier(self):
+        return self._tuple[0]
+
+    def noArguments(self):
+        return len(self._tuple) == 1
+
+    def hasValue(self):
+        return len(self._tuple) >= 2 and isinstance(self._tuple[1], str)
+
+    def value(self):
+        assert(self.hasValue())
+        return self._tuple[1]
+
+    def hasArgs(self):
+        return (len(self._tuple) == 2 and isinstance(self._tuple[1], list) or
+                len(self._tuple) == 3)
+
+    def args(self):
+        assert(self.hasArgs())
+        # Our args are our last element
+        return self._tuple[-1]
+
+    def listValue(self):
+        """
+        Backdoor for storing random data in _extendedAttrDict
+        """
+        return list(self._tuple)[1:]
+
+# Parser
+
+
+class Tokenizer(object):
+    tokens = [
+        "INTEGER",
+        "FLOATLITERAL",
+        "IDENTIFIER",
+        "STRING",
+        "WHITESPACE",
+        "OTHER"
+        ]
+
+    def t_FLOATLITERAL(self, t):
+        r'(-?(([0-9]+\.[0-9]*|[0-9]*\.[0-9]+)([Ee][+-]?[0-9]+)?|[0-9]+[Ee][+-]?[0-9]+|Infinity))|NaN'
+        t.value = float(t.value)
+        return t
+
+    def t_INTEGER(self, t):
+        r'-?(0([0-7]+|[Xx][0-9A-Fa-f]+)?|[1-9][0-9]*)'
+        try:
+            # Can't use int(), because that doesn't handle octal properly.
+            t.value = parseInt(t.value)
+        except:
+            raise WebIDLError("Invalid integer literal",
+                              [Location(lexer=self.lexer,
+                                        lineno=self.lexer.lineno,
+                                        lexpos=self.lexer.lexpos,
+                                        filename=self._filename)])
+        return t
+
+    def t_IDENTIFIER(self, t):
+        r'[A-Z_a-z][0-9A-Z_a-z-]*'
+        t.type = self.keywords.get(t.value, 'IDENTIFIER')
+        return t
+
+    def t_STRING(self, t):
+        r'"[^"]*"'
+        t.value = t.value[1:-1]
+        return t
+
+    def t_WHITESPACE(self, t):
+        r'[\t\n\r ]+|[\t\n\r ]*((//[^\n]*|/\*.*?\*/)[\t\n\r ]*)+'
+        pass
+
+    def t_ELLIPSIS(self, t):
+        r'\.\.\.'
+        t.type = self.keywords.get(t.value)
+        return t
+
+    def t_OTHER(self, t):
+        r'[^\t\n\r 0-9A-Z_a-z]'
+        t.type = self.keywords.get(t.value, 'OTHER')
+        return t
+
+    keywords = {
+        "module": "MODULE",
+        "interface": "INTERFACE",
+        "partial": "PARTIAL",
+        "dictionary": "DICTIONARY",
+        "exception": "EXCEPTION",
+        "enum": "ENUM",
+        "callback": "CALLBACK",
+        "typedef": "TYPEDEF",
+        "implements": "IMPLEMENTS",
+        "const": "CONST",
+        "null": "NULL",
+        "true": "TRUE",
+        "false": "FALSE",
+        "serializer": "SERIALIZER",
+        "stringifier": "STRINGIFIER",
+        "jsonifier": "JSONIFIER",
+        "unrestricted": "UNRESTRICTED",
+        "attribute": "ATTRIBUTE",
+        "readonly": "READONLY",
+        "inherit": "INHERIT",
+        "static": "STATIC",
+        "getter": "GETTER",
+        "setter": "SETTER",
+        "creator": "CREATOR",
+        "deleter": "DELETER",
+        "legacycaller": "LEGACYCALLER",
+        "optional": "OPTIONAL",
+        "...": "ELLIPSIS",
+        "::": "SCOPE",
+        "Date": "DATE",
+        "DOMString": "DOMSTRING",
+        "ByteString": "BYTESTRING",
+        "USVString": "USVSTRING",
+        "any": "ANY",
+        "boolean": "BOOLEAN",
+        "byte": "BYTE",
+        "double": "DOUBLE",
+        "float": "FLOAT",
+        "long": "LONG",
+        "object": "OBJECT",
+        "octet": "OCTET",
+        "Promise": "PROMISE",
+        "required": "REQUIRED",
+        "sequence": "SEQUENCE",
+        "MozMap": "MOZMAP",
+        "short": "SHORT",
+        "unsigned": "UNSIGNED",
+        "void": "VOID",
+        ":": "COLON",
+        ";": "SEMICOLON",
+        "{": "LBRACE",
+        "}": "RBRACE",
+        "(": "LPAREN",
+        ")": "RPAREN",
+        "[": "LBRACKET",
+        "]": "RBRACKET",
+        "?": "QUESTIONMARK",
+        ",": "COMMA",
+        "=": "EQUALS",
+        "<": "LT",
+        ">": "GT",
+        "ArrayBuffer": "ARRAYBUFFER",
+        "SharedArrayBuffer": "SHAREDARRAYBUFFER",
+        "or": "OR",
+        "maplike": "MAPLIKE",
+        "setlike": "SETLIKE",
+        "iterable": "ITERABLE",
+        "namespace": "NAMESPACE"
+        }
+
+    tokens.extend(keywords.values())
+
+    def t_error(self, t):
+        raise WebIDLError("Unrecognized Input",
+                          [Location(lexer=self.lexer,
+                                    lineno=self.lexer.lineno,
+                                    lexpos=self.lexer.lexpos,
+                                    filename=self.filename)])
+
+    def __init__(self, outputdir, lexer=None):
+        if lexer:
+            self.lexer = lexer
+        else:
+            self.lexer = lex.lex(object=self,
+                                 outputdir=outputdir,
+                                 lextab='webidllex',
+                                 reflags=re.DOTALL)
+
+
+class SqueakyCleanLogger(object):
+    errorWhitelist = [
+        # Web IDL defines the WHITESPACE token, but doesn't actually
+        # use it ... so far.
+        "Token 'WHITESPACE' defined, but not used",
+        # And that means we have an unused token
+        "There is 1 unused token",
+        # Web IDL defines a OtherOrComma rule that's only used in
+        # ExtendedAttributeInner, which we don't use yet.
+        "Rule 'OtherOrComma' defined, but not used",
+        # And an unused rule
+        "There is 1 unused rule",
+        # And the OtherOrComma grammar symbol is unreachable.
+        "Symbol 'OtherOrComma' is unreachable",
+        # Which means the Other symbol is unreachable.
+        "Symbol 'Other' is unreachable",
+        ]
+
+    def __init__(self):
+        self.errors = []
+
+    def debug(self, msg, *args, **kwargs):
+        pass
+    info = debug
+
+    def warning(self, msg, *args, **kwargs):
+        if msg == "%s:%d: Rule %r defined, but not used" or \
+           msg == "%s:%d: Rule '%s' defined, but not used":
+            # Munge things so we don't have to hardcode filenames and
+            # line numbers in our whitelist.
+            whitelistmsg = "Rule %r defined, but not used"
+            whitelistargs = args[2:]
+        else:
+            whitelistmsg = msg
+            whitelistargs = args
+        if (whitelistmsg % whitelistargs) not in SqueakyCleanLogger.errorWhitelist:
+            self.errors.append(msg % args)
+    error = warning
+
+    def reportGrammarErrors(self):
+        if self.errors:
+            raise WebIDLError("\n".join(self.errors), [])
+
+
+class Parser(Tokenizer):
+    def getLocation(self, p, i):
+        return Location(self.lexer, p.lineno(i), p.lexpos(i), self._filename)
+
+    def globalScope(self):
+        return self._globalScope
+
+    # The p_Foo functions here must match the WebIDL spec's grammar.
+    # It's acceptable to split things at '|' boundaries.
+    def p_Definitions(self, p):
+        """
+            Definitions : ExtendedAttributeList Definition Definitions
+        """
+        if p[2]:
+            p[0] = [p[2]]
+            p[2].addExtendedAttributes(p[1])
+        else:
+            assert not p[1]
+            p[0] = []
+
+        p[0].extend(p[3])
+
+    def p_DefinitionsEmpty(self, p):
+        """
+            Definitions :
+        """
+        p[0] = []
+
+    def p_Definition(self, p):
+        """
+            Definition : CallbackOrInterface
+                       | Namespace
+                       | Partial
+                       | Dictionary
+                       | Exception
+                       | Enum
+                       | Typedef
+                       | ImplementsStatement
+        """
+        p[0] = p[1]
+        assert p[1]  # We might not have implemented something ...
+
+    def p_CallbackOrInterfaceCallback(self, p):
+        """
+            CallbackOrInterface : CALLBACK CallbackRestOrInterface
+        """
+        if p[2].isInterface():
+            assert isinstance(p[2], IDLInterface)
+            p[2].setCallback(True)
+
+        p[0] = p[2]
+
+    def p_CallbackOrInterfaceInterface(self, p):
+        """
+            CallbackOrInterface : Interface
+        """
+        p[0] = p[1]
+
+    def p_CallbackRestOrInterface(self, p):
+        """
+            CallbackRestOrInterface : CallbackRest
+                                    | Interface
+        """
+        assert p[1]
+        p[0] = p[1]
+
+    def handleNonPartialObject(self, location, identifier, constructor,
+                               constructorArgs, nonPartialArgs):
+        """
+        This handles non-partial objects (interfaces and namespaces) by
+        checking for an existing partial object, and promoting it to
+        non-partial as needed.  The return value is the non-partial object.
+
+        constructorArgs are all the args for the constructor except the last
+        one: isKnownNonPartial.
+
+        nonPartialArgs are the args for the setNonPartial call.
+        """
+        # The name of the class starts with "IDL", so strip that off.
+        # Also, starts with a capital letter after that, so nix that
+        # as well.
+        prettyname = constructor.__name__[3:].lower()
+
+        try:
+            existingObj = self.globalScope()._lookupIdentifier(identifier)
+            if existingObj:
+                if not isinstance(existingObj, constructor):
+                    raise WebIDLError("%s has the same name as "
+                                      "non-%s object" %
+                                      (prettyname.capitalize(), prettyname),
+                                      [location, existingObj.location])
+                existingObj.setNonPartial(*nonPartialArgs)
+                return existingObj
+        except Exception, ex:
+            if isinstance(ex, WebIDLError):
+                raise ex
+            pass
+
+        # True for isKnownNonPartial
+        return constructor(*(constructorArgs + [True]))
+
+    def p_Interface(self, p):
+        """
+            Interface : INTERFACE IDENTIFIER Inheritance LBRACE InterfaceMembers RBRACE SEMICOLON
+        """
+        location = self.getLocation(p, 1)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 2), p[2])
+        members = p[5]
+        parent = p[3]
+
+        p[0] = self.handleNonPartialObject(
+            location, identifier, IDLInterface,
+            [location, self.globalScope(), identifier, parent, members],
+            [location, parent, members])
+
+    def p_InterfaceForwardDecl(self, p):
+        """
+            Interface : INTERFACE IDENTIFIER SEMICOLON
+        """
+        location = self.getLocation(p, 1)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 2), p[2])
+
+        try:
+            if self.globalScope()._lookupIdentifier(identifier):
+                p[0] = self.globalScope()._lookupIdentifier(identifier)
+                if not isinstance(p[0], IDLExternalInterface):
+                    raise WebIDLError("Name collision between external "
+                                      "interface declaration for identifier "
+                                      "%s and %s" % (identifier.name, p[0]),
+                                      [location, p[0].location])
+                return
+        except Exception, ex:
+            if isinstance(ex, WebIDLError):
+                raise ex
+            pass
+
+        p[0] = IDLExternalInterface(location, self.globalScope(), identifier)
+
+    def p_Namespace(self, p):
+        """
+            Namespace : NAMESPACE IDENTIFIER LBRACE InterfaceMembers RBRACE SEMICOLON
+        """
+        location = self.getLocation(p, 1)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 2), p[2])
+        members = p[4]
+
+        p[0] = self.handleNonPartialObject(
+            location, identifier, IDLNamespace,
+            [location, self.globalScope(), identifier, members],
+            [location, None, members])
+
+    def p_Partial(self, p):
+        """
+            Partial : PARTIAL PartialDefinition
+        """
+        p[0] = p[2]
+
+    def p_PartialDefinition(self, p):
+        """
+            PartialDefinition : PartialInterface
+                              | PartialNamespace
+        """
+        p[0] = p[1]
+
+    def handlePartialObject(self, location, identifier, nonPartialConstructor,
+                            nonPartialConstructorArgs,
+                            partialConstructorArgs):
+        """
+        This handles partial objects (interfaces and namespaces) by checking for
+        an existing non-partial object, and adding ourselves to it as needed.
+        The return value is our partial object.  For now we just use
+        IDLPartialInterfaceOrNamespace for partial objects.
+
+        nonPartialConstructorArgs are all the args for the non-partial
+        constructor except the last two: members and isKnownNonPartial.
+
+        partialConstructorArgs are the arguments for the
+        IDLPartialInterfaceOrNamespace constructor, except the last one (the
+        non-partial object).
+        """
+        # The name of the class starts with "IDL", so strip that off.
+        # Also, starts with a capital letter after that, so nix that
+        # as well.
+        prettyname = nonPartialConstructor.__name__[3:].lower()
+
+        nonPartialObject = None
+        try:
+            nonPartialObject = self.globalScope()._lookupIdentifier(identifier)
+            if nonPartialObject:
+                if not isinstance(nonPartialObject, nonPartialConstructor):
+                    raise WebIDLError("Partial %s has the same name as "
+                                      "non-%s object" %
+                                      (prettyname, prettyname),
+                                      [location, nonPartialObject.location])
+        except Exception, ex:
+            if isinstance(ex, WebIDLError):
+                raise ex
+            pass
+
+        if not nonPartialObject:
+            nonPartialObject = nonPartialConstructor(
+                # No members, False for isKnownNonPartial
+                *(nonPartialConstructorArgs + [[], False]))
+        partialInterface = IDLPartialInterfaceOrNamespace(
+            *(partialConstructorArgs + [nonPartialObject]))
+        return partialInterface
+
+    def p_PartialInterface(self, p):
+        """
+            PartialInterface : INTERFACE IDENTIFIER LBRACE InterfaceMembers RBRACE SEMICOLON
+        """
+        location = self.getLocation(p, 1)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 2), p[2])
+        members = p[4]
+
+        p[0] = self.handlePartialObject(
+            location, identifier, IDLInterface,
+            [location, self.globalScope(), identifier, None],
+            [location, identifier, members])
+
+    def p_PartialNamespace(self, p):
+        """
+            PartialNamespace : NAMESPACE IDENTIFIER LBRACE InterfaceMembers RBRACE SEMICOLON
+        """
+        location = self.getLocation(p, 1)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 2), p[2])
+        members = p[4]
+
+        p[0] = self.handlePartialObject(
+            location, identifier, IDLNamespace,
+            [location, self.globalScope(), identifier],
+            [location, identifier, members])
+
+    def p_Inheritance(self, p):
+        """
+            Inheritance : COLON ScopedName
+        """
+        p[0] = IDLIdentifierPlaceholder(self.getLocation(p, 2), p[2])
+
+    def p_InheritanceEmpty(self, p):
+        """
+            Inheritance :
+        """
+        pass
+
+    def p_InterfaceMembers(self, p):
+        """
+            InterfaceMembers : ExtendedAttributeList InterfaceMember InterfaceMembers
+        """
+        p[0] = [p[2]] if p[2] else []
+
+        assert not p[1] or p[2]
+        p[2].addExtendedAttributes(p[1])
+
+        p[0].extend(p[3])
+
+    def p_InterfaceMembersEmpty(self, p):
+        """
+            InterfaceMembers :
+        """
+        p[0] = []
+
+    def p_InterfaceMember(self, p):
+        """
+            InterfaceMember : Const
+                            | AttributeOrOperationOrMaplikeOrSetlikeOrIterable
+        """
+        p[0] = p[1]
+
+    def p_Dictionary(self, p):
+        """
+            Dictionary : DICTIONARY IDENTIFIER Inheritance LBRACE DictionaryMembers RBRACE SEMICOLON
+        """
+        location = self.getLocation(p, 1)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 2), p[2])
+        members = p[5]
+        p[0] = IDLDictionary(location, self.globalScope(), identifier, p[3], members)
+
+    def p_DictionaryMembers(self, p):
+        """
+            DictionaryMembers : ExtendedAttributeList DictionaryMember DictionaryMembers
+                             |
+        """
+        if len(p) == 1:
+            # We're at the end of the list
+            p[0] = []
+            return
+        # Add our extended attributes
+        p[2].addExtendedAttributes(p[1])
+        p[0] = [p[2]]
+        p[0].extend(p[3])
+
+    def p_DictionaryMember(self, p):
+        """
+            DictionaryMember : Required Type IDENTIFIER Default SEMICOLON
+        """
+        # These quack a lot like optional arguments, so just treat them that way.
+        t = p[2]
+        assert isinstance(t, IDLType)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 3), p[3])
+        defaultValue = p[4]
+        optional = not p[1]
+
+        if not optional and defaultValue:
+            raise WebIDLError("Required dictionary members can't have a default value.",
+                              [self.getLocation(p, 4)])
+
+        p[0] = IDLArgument(self.getLocation(p, 3), identifier, t,
+                           optional=optional,
+                           defaultValue=defaultValue, variadic=False,
+                           dictionaryMember=True)
+
+    def p_Default(self, p):
+        """
+            Default : EQUALS DefaultValue
+                    |
+        """
+        if len(p) > 1:
+            p[0] = p[2]
+        else:
+            p[0] = None
+
+    def p_DefaultValue(self, p):
+        """
+            DefaultValue : ConstValue
+                         | LBRACKET RBRACKET
+        """
+        if len(p) == 2:
+            p[0] = p[1]
+        else:
+            assert len(p) == 3  # Must be []
+            p[0] = IDLEmptySequenceValue(self.getLocation(p, 1))
+
+    def p_Exception(self, p):
+        """
+            Exception : EXCEPTION IDENTIFIER Inheritance LBRACE ExceptionMembers RBRACE SEMICOLON
+        """
+        pass
+
+    def p_Enum(self, p):
+        """
+            Enum : ENUM IDENTIFIER LBRACE EnumValueList RBRACE SEMICOLON
+        """
+        location = self.getLocation(p, 1)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 2), p[2])
+
+        values = p[4]
+        assert values
+        p[0] = IDLEnum(location, self.globalScope(), identifier, values)
+
+    def p_EnumValueList(self, p):
+        """
+            EnumValueList : STRING EnumValueListComma
+        """
+        p[0] = [p[1]]
+        p[0].extend(p[2])
+
+    def p_EnumValueListComma(self, p):
+        """
+            EnumValueListComma : COMMA EnumValueListString
+        """
+        p[0] = p[2]
+
+    def p_EnumValueListCommaEmpty(self, p):
+        """
+            EnumValueListComma :
+        """
+        p[0] = []
+
+    def p_EnumValueListString(self, p):
+        """
+            EnumValueListString : STRING EnumValueListComma
+        """
+        p[0] = [p[1]]
+        p[0].extend(p[2])
+
+    def p_EnumValueListStringEmpty(self, p):
+        """
+            EnumValueListString :
+        """
+        p[0] = []
+
+    def p_CallbackRest(self, p):
+        """
+            CallbackRest : IDENTIFIER EQUALS ReturnType LPAREN ArgumentList RPAREN SEMICOLON
+        """
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 1), p[1])
+        p[0] = IDLCallback(self.getLocation(p, 1), self.globalScope(),
+                           identifier, p[3], p[5])
+
+    def p_ExceptionMembers(self, p):
+        """
+            ExceptionMembers : ExtendedAttributeList ExceptionMember ExceptionMembers
+                             |
+        """
+        pass
+
+    def p_Typedef(self, p):
+        """
+            Typedef : TYPEDEF Type IDENTIFIER SEMICOLON
+        """
+        typedef = IDLTypedef(self.getLocation(p, 1), self.globalScope(),
+                             p[2], p[3])
+        p[0] = typedef
+
+    def p_ImplementsStatement(self, p):
+        """
+            ImplementsStatement : ScopedName IMPLEMENTS ScopedName SEMICOLON
+        """
+        assert(p[2] == "implements")
+        implementor = IDLIdentifierPlaceholder(self.getLocation(p, 1), p[1])
+        implementee = IDLIdentifierPlaceholder(self.getLocation(p, 3), p[3])
+        p[0] = IDLImplementsStatement(self.getLocation(p, 1), implementor,
+                                      implementee)
+
+    def p_Const(self, p):
+        """
+            Const : CONST ConstType IDENTIFIER EQUALS ConstValue SEMICOLON
+        """
+        location = self.getLocation(p, 1)
+        type = p[2]
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 3), p[3])
+        value = p[5]
+        p[0] = IDLConst(location, identifier, type, value)
+
+    def p_ConstValueBoolean(self, p):
+        """
+            ConstValue : BooleanLiteral
+        """
+        location = self.getLocation(p, 1)
+        booleanType = BuiltinTypes[IDLBuiltinType.Types.boolean]
+        p[0] = IDLValue(location, booleanType, p[1])
+
+    def p_ConstValueInteger(self, p):
+        """
+            ConstValue : INTEGER
+        """
+        location = self.getLocation(p, 1)
+
+        # We don't know ahead of time what type the integer literal is.
+        # Determine the smallest type it could possibly fit in and use that.
+        integerType = matchIntegerValueToType(p[1])
+        if integerType is None:
+            raise WebIDLError("Integer literal out of range", [location])
+
+        p[0] = IDLValue(location, integerType, p[1])
+
+    def p_ConstValueFloat(self, p):
+        """
+            ConstValue : FLOATLITERAL
+        """
+        location = self.getLocation(p, 1)
+        p[0] = IDLValue(location, BuiltinTypes[IDLBuiltinType.Types.unrestricted_float], p[1])
+
+    def p_ConstValueString(self, p):
+        """
+            ConstValue : STRING
+        """
+        location = self.getLocation(p, 1)
+        stringType = BuiltinTypes[IDLBuiltinType.Types.domstring]
+        p[0] = IDLValue(location, stringType, p[1])
+
+    def p_ConstValueNull(self, p):
+        """
+            ConstValue : NULL
+        """
+        p[0] = IDLNullValue(self.getLocation(p, 1))
+
+    def p_BooleanLiteralTrue(self, p):
+        """
+            BooleanLiteral : TRUE
+        """
+        p[0] = True
+
+    def p_BooleanLiteralFalse(self, p):
+        """
+            BooleanLiteral : FALSE
+        """
+        p[0] = False
+
+    def p_AttributeOrOperationOrMaplikeOrSetlikeOrIterable(self, p):
+        """
+            AttributeOrOperationOrMaplikeOrSetlikeOrIterable : Attribute
+                                                             | Maplike
+                                                             | Setlike
+                                                             | Iterable
+                                                             | Operation
+        """
+        p[0] = p[1]
+
+    def p_Iterable(self, p):
+        """
+            Iterable : ITERABLE LT Type GT SEMICOLON
+                     | ITERABLE LT Type COMMA Type GT SEMICOLON
+        """
+        location = self.getLocation(p, 2)
+        identifier = IDLUnresolvedIdentifier(location, "__iterable",
+                                             allowDoubleUnderscore=True)
+        if (len(p) > 6):
+            keyType = p[3]
+            valueType = p[5]
+        else:
+            keyType = None
+            valueType = p[3]
+
+        p[0] = IDLIterable(location, identifier, keyType, valueType, self.globalScope())
+
+    def p_Setlike(self, p):
+        """
+            Setlike : ReadOnly SETLIKE LT Type GT SEMICOLON
+        """
+        readonly = p[1]
+        maplikeOrSetlikeType = p[2]
+        location = self.getLocation(p, 2)
+        identifier = IDLUnresolvedIdentifier(location, "__setlike",
+                                             allowDoubleUnderscore=True)
+        keyType = p[4]
+        valueType = keyType
+        p[0] = IDLMaplikeOrSetlike(location, identifier, maplikeOrSetlikeType,
+                                   readonly, keyType, valueType)
+
+    def p_Maplike(self, p):
+        """
+            Maplike : ReadOnly MAPLIKE LT Type COMMA Type GT SEMICOLON
+        """
+        readonly = p[1]
+        maplikeOrSetlikeType = p[2]
+        location = self.getLocation(p, 2)
+        identifier = IDLUnresolvedIdentifier(location, "__maplike",
+                                             allowDoubleUnderscore=True)
+        keyType = p[4]
+        valueType = p[6]
+        p[0] = IDLMaplikeOrSetlike(location, identifier, maplikeOrSetlikeType,
+                                   readonly, keyType, valueType)
+
+    def p_AttributeWithQualifier(self, p):
+        """
+            Attribute : Qualifier AttributeRest
+        """
+        static = IDLInterfaceMember.Special.Static in p[1]
+        stringifier = IDLInterfaceMember.Special.Stringifier in p[1]
+        (location, identifier, type, readonly) = p[2]
+        p[0] = IDLAttribute(location, identifier, type, readonly,
+                            static=static, stringifier=stringifier)
+
+    def p_AttributeInherited(self, p):
+        """
+            Attribute : INHERIT AttributeRest
+        """
+        (location, identifier, type, readonly) = p[2]
+        p[0] = IDLAttribute(location, identifier, type, readonly, inherit=True)
+
+    def p_Attribute(self, p):
+        """
+            Attribute : AttributeRest
+        """
+        (location, identifier, type, readonly) = p[1]
+        p[0] = IDLAttribute(location, identifier, type, readonly, inherit=False)
+
+    def p_AttributeRest(self, p):
+        """
+            AttributeRest : ReadOnly ATTRIBUTE Type AttributeName SEMICOLON
+        """
+        location = self.getLocation(p, 2)
+        readonly = p[1]
+        t = p[3]
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 4), p[4])
+        p[0] = (location, identifier, t, readonly)
+
+    def p_ReadOnly(self, p):
+        """
+            ReadOnly : READONLY
+        """
+        p[0] = True
+
+    def p_ReadOnlyEmpty(self, p):
+        """
+            ReadOnly :
+        """
+        p[0] = False
+
+    def p_Operation(self, p):
+        """
+            Operation : Qualifiers OperationRest
+        """
+        qualifiers = p[1]
+
+        # Disallow duplicates in the qualifier set
+        if not len(set(qualifiers)) == len(qualifiers):
+            raise WebIDLError("Duplicate qualifiers are not allowed",
+                              [self.getLocation(p, 1)])
+
+        static = IDLInterfaceMember.Special.Static in p[1]
+        # If static is there that's all that's allowed.  This is disallowed
+        # by the parser, so we can assert here.
+        assert not static or len(qualifiers) == 1
+
+        stringifier = IDLInterfaceMember.Special.Stringifier in p[1]
+        # If stringifier is there that's all that's allowed.  This is disallowed
+        # by the parser, so we can assert here.
+        assert not stringifier or len(qualifiers) == 1
+
+        getter = True if IDLMethod.Special.Getter in p[1] else False
+        setter = True if IDLMethod.Special.Setter in p[1] else False
+        creator = True if IDLMethod.Special.Creator in p[1] else False
+        deleter = True if IDLMethod.Special.Deleter in p[1] else False
+        legacycaller = True if IDLMethod.Special.LegacyCaller in p[1] else False
+
+        if getter or deleter:
+            if setter or creator:
+                raise WebIDLError("getter and deleter are incompatible with setter and creator",
+                                  [self.getLocation(p, 1)])
+
+        (returnType, identifier, arguments) = p[2]
+
+        assert isinstance(returnType, IDLType)
+
+        specialType = IDLMethod.NamedOrIndexed.Neither
+
+        if getter or deleter:
+            if len(arguments) != 1:
+                raise WebIDLError("%s has wrong number of arguments" %
+                                  ("getter" if getter else "deleter"),
+                                  [self.getLocation(p, 2)])
+            argType = arguments[0].type
+            if argType == BuiltinTypes[IDLBuiltinType.Types.domstring]:
+                specialType = IDLMethod.NamedOrIndexed.Named
+            elif argType == BuiltinTypes[IDLBuiltinType.Types.unsigned_long]:
+                specialType = IDLMethod.NamedOrIndexed.Indexed
+                if deleter:
+                    raise WebIDLError("There is no such thing as an indexed deleter.",
+                                      [self.getLocation(p, 1)])
+            else:
+                raise WebIDLError("%s has wrong argument type (must be DOMString or UnsignedLong)" %
+                                  ("getter" if getter else "deleter"),
+                                  [arguments[0].location])
+            if arguments[0].optional or arguments[0].variadic:
+                raise WebIDLError("%s cannot have %s argument" %
+                                  ("getter" if getter else "deleter",
+                                   "optional" if arguments[0].optional else "variadic"),
+                                  [arguments[0].location])
+        if getter:
+            if returnType.isVoid():
+                raise WebIDLError("getter cannot have void return type",
+                                  [self.getLocation(p, 2)])
+        if setter or creator:
+            if len(arguments) != 2:
+                raise WebIDLError("%s has wrong number of arguments" %
+                                  ("setter" if setter else "creator"),
+                                  [self.getLocation(p, 2)])
+            argType = arguments[0].type
+            if argType == BuiltinTypes[IDLBuiltinType.Types.domstring]:
+                specialType = IDLMethod.NamedOrIndexed.Named
+            elif argType == BuiltinTypes[IDLBuiltinType.Types.unsigned_long]:
+                specialType = IDLMethod.NamedOrIndexed.Indexed
+            else:
+                raise WebIDLError("%s has wrong argument type (must be DOMString or UnsignedLong)" %
+                                  ("setter" if setter else "creator"),
+                                  [arguments[0].location])
+            if arguments[0].optional or arguments[0].variadic:
+                raise WebIDLError("%s cannot have %s argument" %
+                                  ("setter" if setter else "creator",
+                                   "optional" if arguments[0].optional else "variadic"),
+                                  [arguments[0].location])
+            if arguments[1].optional or arguments[1].variadic:
+                raise WebIDLError("%s cannot have %s argument" %
+                                  ("setter" if setter else "creator",
+                                   "optional" if arguments[1].optional else "variadic"),
+                                  [arguments[1].location])
+
+        if stringifier:
+            if len(arguments) != 0:
+                raise WebIDLError("stringifier has wrong number of arguments",
+                                  [self.getLocation(p, 2)])
+            if not returnType.isDOMString():
+                raise WebIDLError("stringifier must have DOMString return type",
+                                  [self.getLocation(p, 2)])
+
+        # identifier might be None.  This is only permitted for special methods.
+        if not identifier:
+            if (not getter and not setter and not creator and
+                not deleter and not legacycaller and not stringifier):
+                raise WebIDLError("Identifier required for non-special methods",
+                                  [self.getLocation(p, 2)])
+
+            location = BuiltinLocation("<auto-generated-identifier>")
+            identifier = IDLUnresolvedIdentifier(
+                location,
+                "__%s%s%s%s%s%s%s" %
+                ("named" if specialType == IDLMethod.NamedOrIndexed.Named else
+                 "indexed" if specialType == IDLMethod.NamedOrIndexed.Indexed else "",
+                 "getter" if getter else "",
+                 "setter" if setter else "",
+                 "deleter" if deleter else "",
+                 "creator" if creator else "",
+                 "legacycaller" if legacycaller else "",
+                 "stringifier" if stringifier else ""),
+                allowDoubleUnderscore=True)
+
+        method = IDLMethod(self.getLocation(p, 2), identifier, returnType, arguments,
+                           static=static, getter=getter, setter=setter, creator=creator,
+                           deleter=deleter, specialType=specialType,
+                           legacycaller=legacycaller, stringifier=stringifier)
+        p[0] = method
+
+    def p_Stringifier(self, p):
+        """
+            Operation : STRINGIFIER SEMICOLON
+        """
+        identifier = IDLUnresolvedIdentifier(BuiltinLocation("<auto-generated-identifier>"),
+                                             "__stringifier",
+                                             allowDoubleUnderscore=True)
+        method = IDLMethod(self.getLocation(p, 1),
+                           identifier,
+                           returnType=BuiltinTypes[IDLBuiltinType.Types.domstring],
+                           arguments=[],
+                           stringifier=True)
+        p[0] = method
+
+    def p_Jsonifier(self, p):
+        """
+            Operation : JSONIFIER SEMICOLON
+        """
+        identifier = IDLUnresolvedIdentifier(BuiltinLocation("<auto-generated-identifier>"),
+                                             "__jsonifier", allowDoubleUnderscore=True)
+        method = IDLMethod(self.getLocation(p, 1),
+                           identifier,
+                           returnType=BuiltinTypes[IDLBuiltinType.Types.object],
+                           arguments=[],
+                           jsonifier=True)
+        p[0] = method
+
+    def p_QualifierStatic(self, p):
+        """
+            Qualifier : STATIC
+        """
+        p[0] = [IDLInterfaceMember.Special.Static]
+
+    def p_QualifierStringifier(self, p):
+        """
+            Qualifier : STRINGIFIER
+        """
+        p[0] = [IDLInterfaceMember.Special.Stringifier]
+
+    def p_Qualifiers(self, p):
+        """
+            Qualifiers : Qualifier
+                       | Specials
+        """
+        p[0] = p[1]
+
+    def p_Specials(self, p):
+        """
+            Specials : Special Specials
+        """
+        p[0] = [p[1]]
+        p[0].extend(p[2])
+
+    def p_SpecialsEmpty(self, p):
+        """
+            Specials :
+        """
+        p[0] = []
+
+    def p_SpecialGetter(self, p):
+        """
+            Special : GETTER
+        """
+        p[0] = IDLMethod.Special.Getter
+
+    def p_SpecialSetter(self, p):
+        """
+            Special : SETTER
+        """
+        p[0] = IDLMethod.Special.Setter
+
+    def p_SpecialCreator(self, p):
+        """
+            Special : CREATOR
+        """
+        p[0] = IDLMethod.Special.Creator
+
+    def p_SpecialDeleter(self, p):
+        """
+            Special : DELETER
+        """
+        p[0] = IDLMethod.Special.Deleter
+
+    def p_SpecialLegacyCaller(self, p):
+        """
+            Special : LEGACYCALLER
+        """
+        p[0] = IDLMethod.Special.LegacyCaller
+
+    def p_OperationRest(self, p):
+        """
+            OperationRest : ReturnType OptionalIdentifier LPAREN ArgumentList RPAREN SEMICOLON
+        """
+        p[0] = (p[1], p[2], p[4])
+
+    def p_OptionalIdentifier(self, p):
+        """
+            OptionalIdentifier : IDENTIFIER
+        """
+        p[0] = IDLUnresolvedIdentifier(self.getLocation(p, 1), p[1])
+
+    def p_OptionalIdentifierEmpty(self, p):
+        """
+            OptionalIdentifier :
+        """
+        pass
+
+    def p_ArgumentList(self, p):
+        """
+            ArgumentList : Argument Arguments
+        """
+        p[0] = [p[1]] if p[1] else []
+        p[0].extend(p[2])
+
+    def p_ArgumentListEmpty(self, p):
+        """
+            ArgumentList :
+        """
+        p[0] = []
+
+    def p_Arguments(self, p):
+        """
+            Arguments : COMMA Argument Arguments
+        """
+        p[0] = [p[2]] if p[2] else []
+        p[0].extend(p[3])
+
+    def p_ArgumentsEmpty(self, p):
+        """
+            Arguments :
+        """
+        p[0] = []
+
+    def p_Argument(self, p):
+        """
+            Argument : ExtendedAttributeList Optional Type Ellipsis ArgumentName Default
+        """
+        t = p[3]
+        assert isinstance(t, IDLType)
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 5), p[5])
+
+        optional = p[2]
+        variadic = p[4]
+        defaultValue = p[6]
+
+        if not optional and defaultValue:
+            raise WebIDLError("Mandatory arguments can't have a default value.",
+                              [self.getLocation(p, 6)])
+
+        # We can't test t.isAny() here and give it a default value as needed,
+        # since at this point t is not a fully resolved type yet (e.g. it might
+        # be a typedef).  We'll handle the 'any' case in IDLArgument.complete.
+
+        if variadic:
+            if optional:
+                raise WebIDLError("Variadic arguments should not be marked optional.",
+                                  [self.getLocation(p, 2)])
+            optional = variadic
+
+        p[0] = IDLArgument(self.getLocation(p, 5), identifier, t, optional, defaultValue, variadic)
+        p[0].addExtendedAttributes(p[1])
+
+    def p_ArgumentName(self, p):
+        """
+            ArgumentName : IDENTIFIER
+                         | ATTRIBUTE
+                         | CALLBACK
+                         | CONST
+                         | CREATOR
+                         | DELETER
+                         | DICTIONARY
+                         | ENUM
+                         | EXCEPTION
+                         | GETTER
+                         | IMPLEMENTS
+                         | INHERIT
+                         | INTERFACE
+                         | ITERABLE
+                         | LEGACYCALLER
+                         | MAPLIKE
+                         | PARTIAL
+                         | REQUIRED
+                         | SERIALIZER
+                         | SETLIKE
+                         | SETTER
+                         | STATIC
+                         | STRINGIFIER
+                         | JSONIFIER
+                         | TYPEDEF
+                         | UNRESTRICTED
+                         | NAMESPACE
+        """
+        p[0] = p[1]
+
+    def p_AttributeName(self, p):
+        """
+            AttributeName : IDENTIFIER
+                          | REQUIRED
+        """
+        p[0] = p[1]
+
+    def p_Optional(self, p):
+        """
+            Optional : OPTIONAL
+        """
+        p[0] = True
+
+    def p_OptionalEmpty(self, p):
+        """
+            Optional :
+        """
+        p[0] = False
+
+    def p_Required(self, p):
+        """
+            Required : REQUIRED
+        """
+        p[0] = True
+
+    def p_RequiredEmpty(self, p):
+        """
+            Required :
+        """
+        p[0] = False
+
+    def p_Ellipsis(self, p):
+        """
+            Ellipsis : ELLIPSIS
+        """
+        p[0] = True
+
+    def p_EllipsisEmpty(self, p):
+        """
+            Ellipsis :
+        """
+        p[0] = False
+
+    def p_ExceptionMember(self, p):
+        """
+            ExceptionMember : Const
+                            | ExceptionField
+        """
+        pass
+
+    def p_ExceptionField(self, p):
+        """
+            ExceptionField : Type IDENTIFIER SEMICOLON
+        """
+        pass
+
+    def p_ExtendedAttributeList(self, p):
+        """
+            ExtendedAttributeList : LBRACKET ExtendedAttribute ExtendedAttributes RBRACKET
+        """
+        p[0] = [p[2]]
+        if p[3]:
+            p[0].extend(p[3])
+
+    def p_ExtendedAttributeListEmpty(self, p):
+        """
+            ExtendedAttributeList :
+        """
+        p[0] = []
+
+    def p_ExtendedAttribute(self, p):
+        """
+            ExtendedAttribute : ExtendedAttributeNoArgs
+                              | ExtendedAttributeArgList
+                              | ExtendedAttributeIdent
+                              | ExtendedAttributeNamedArgList
+                              | ExtendedAttributeIdentList
+        """
+        p[0] = IDLExtendedAttribute(self.getLocation(p, 1), p[1])
+
+    def p_ExtendedAttributeEmpty(self, p):
+        """
+            ExtendedAttribute :
+        """
+        pass
+
+    def p_ExtendedAttributes(self, p):
+        """
+            ExtendedAttributes : COMMA ExtendedAttribute ExtendedAttributes
+        """
+        p[0] = [p[2]] if p[2] else []
+        p[0].extend(p[3])
+
+    def p_ExtendedAttributesEmpty(self, p):
+        """
+            ExtendedAttributes :
+        """
+        p[0] = []
+
+    def p_Other(self, p):
+        """
+            Other : INTEGER
+                  | FLOATLITERAL
+                  | IDENTIFIER
+                  | STRING
+                  | OTHER
+                  | ELLIPSIS
+                  | COLON
+                  | SCOPE
+                  | SEMICOLON
+                  | LT
+                  | EQUALS
+                  | GT
+                  | QUESTIONMARK
+                  | DATE
+                  | DOMSTRING
+                  | BYTESTRING
+                  | USVSTRING
+                  | ANY
+                  | ATTRIBUTE
+                  | BOOLEAN
+                  | BYTE
+                  | LEGACYCALLER
+                  | CONST
+                  | CREATOR
+                  | DELETER
+                  | DOUBLE
+                  | EXCEPTION
+                  | FALSE
+                  | FLOAT
+                  | GETTER
+                  | IMPLEMENTS
+                  | INHERIT
+                  | INTERFACE
+                  | LONG
+                  | MODULE
+                  | NULL
+                  | OBJECT
+                  | OCTET
+                  | OPTIONAL
+                  | SEQUENCE
+                  | MOZMAP
+                  | SETTER
+                  | SHORT
+                  | STATIC
+                  | STRINGIFIER
+                  | JSONIFIER
+                  | TRUE
+                  | TYPEDEF
+                  | UNSIGNED
+                  | VOID
+        """
+        pass
+
+    def p_OtherOrComma(self, p):
+        """
+            OtherOrComma : Other
+                         | COMMA
+        """
+        pass
+
+    def p_TypeSingleType(self, p):
+        """
+            Type : SingleType
+        """
+        p[0] = p[1]
+
+    def p_TypeUnionType(self, p):
+        """
+            Type : UnionType Null
+        """
+        p[0] = self.handleNullable(p[1], p[2])
+
+    def p_SingleTypeNonAnyType(self, p):
+        """
+            SingleType : NonAnyType
+        """
+        p[0] = p[1]
+
+    def p_SingleTypeAnyType(self, p):
+        """
+            SingleType : ANY
+        """
+        p[0] = BuiltinTypes[IDLBuiltinType.Types.any]
+
+    def p_UnionType(self, p):
+        """
+            UnionType : LPAREN UnionMemberType OR UnionMemberType UnionMemberTypes RPAREN
+        """
+        types = [p[2], p[4]]
+        types.extend(p[5])
+        p[0] = IDLUnionType(self.getLocation(p, 1), types)
+
+    def p_UnionMemberTypeNonAnyType(self, p):
+        """
+            UnionMemberType : NonAnyType
+        """
+        p[0] = p[1]
+
+    def p_UnionMemberType(self, p):
+        """
+            UnionMemberType : UnionType Null
+        """
+        p[0] = self.handleNullable(p[1], p[2])
+
+    def p_UnionMemberTypes(self, p):
+        """
+            UnionMemberTypes : OR UnionMemberType UnionMemberTypes
+        """
+        p[0] = [p[2]]
+        p[0].extend(p[3])
+
+    def p_UnionMemberTypesEmpty(self, p):
+        """
+            UnionMemberTypes :
+        """
+        p[0] = []
+
+    def p_NonAnyType(self, p):
+        """
+            NonAnyType : PrimitiveOrStringType Null
+                       | ARRAYBUFFER Null
+                       | SHAREDARRAYBUFFER Null
+                       | OBJECT Null
+        """
+        if p[1] == "object":
+            type = BuiltinTypes[IDLBuiltinType.Types.object]
+        elif p[1] == "ArrayBuffer":
+            type = BuiltinTypes[IDLBuiltinType.Types.ArrayBuffer]
+        elif p[1] == "SharedArrayBuffer":
+            type = BuiltinTypes[IDLBuiltinType.Types.SharedArrayBuffer]
+        else:
+            type = BuiltinTypes[p[1]]
+
+        p[0] = self.handleNullable(type, p[2])
+
+    def p_NonAnyTypeSequenceType(self, p):
+        """
+            NonAnyType : SEQUENCE LT Type GT Null
+        """
+        innerType = p[3]
+        type = IDLSequenceType(self.getLocation(p, 1), innerType)
+        p[0] = self.handleNullable(type, p[5])
+
+    # Note: Promise<void> is allowed, so we want to parametrize on
+    # ReturnType, not Type.  Also, we want this to end up picking up
+    # the Promise interface for now, hence the games with IDLUnresolvedType.
+    def p_NonAnyTypePromiseType(self, p):
+        """
+            NonAnyType : PROMISE LT ReturnType GT Null
+        """
+        innerType = p[3]
+        promiseIdent = IDLUnresolvedIdentifier(self.getLocation(p, 1), "Promise")
+        type = IDLUnresolvedType(self.getLocation(p, 1), promiseIdent, p[3])
+        p[0] = self.handleNullable(type, p[5])
+
+    def p_NonAnyTypeMozMapType(self, p):
+        """
+            NonAnyType : MOZMAP LT Type GT Null
+        """
+        innerType = p[3]
+        type = IDLMozMapType(self.getLocation(p, 1), innerType)
+        p[0] = self.handleNullable(type, p[5])
+
+    def p_NonAnyTypeScopedName(self, p):
+        """
+            NonAnyType : ScopedName Null
+        """
+        assert isinstance(p[1], IDLUnresolvedIdentifier)
+
+        if p[1].name == "Promise":
+            raise WebIDLError("Promise used without saying what it's "
+                              "parametrized over",
+                              [self.getLocation(p, 1)])
+
+        type = None
+
+        try:
+            if self.globalScope()._lookupIdentifier(p[1]):
+                obj = self.globalScope()._lookupIdentifier(p[1])
+                assert not obj.isType()
+                if obj.isTypedef():
+                    type = IDLTypedefType(self.getLocation(p, 1), obj.innerType,
+                                          obj.identifier.name)
+                elif obj.isCallback() and not obj.isInterface():
+                    type = IDLCallbackType(self.getLocation(p, 1), obj)
+                else:
+                    type = IDLWrapperType(self.getLocation(p, 1), p[1])
+                p[0] = self.handleNullable(type, p[2])
+                return
+        except:
+            pass
+
+        type = IDLUnresolvedType(self.getLocation(p, 1), p[1])
+        p[0] = self.handleNullable(type, p[2])
+
+    def p_NonAnyTypeDate(self, p):
+        """
+            NonAnyType : DATE Null
+        """
+        p[0] = self.handleNullable(BuiltinTypes[IDLBuiltinType.Types.date],
+                                   p[2])
+
+    def p_ConstType(self, p):
+        """
+            ConstType : PrimitiveOrStringType Null
+        """
+        type = BuiltinTypes[p[1]]
+        p[0] = self.handleNullable(type, p[2])
+
+    def p_ConstTypeIdentifier(self, p):
+        """
+            ConstType : IDENTIFIER Null
+        """
+        identifier = IDLUnresolvedIdentifier(self.getLocation(p, 1), p[1])
+
+        type = IDLUnresolvedType(self.getLocation(p, 1), identifier)
+        p[0] = self.handleNullable(type, p[2])
+
+    def p_PrimitiveOrStringTypeUint(self, p):
+        """
+            PrimitiveOrStringType : UnsignedIntegerType
+        """
+        p[0] = p[1]
+
+    def p_PrimitiveOrStringTypeBoolean(self, p):
+        """
+            PrimitiveOrStringType : BOOLEAN
+        """
+        p[0] = IDLBuiltinType.Types.boolean
+
+    def p_PrimitiveOrStringTypeByte(self, p):
+        """
+            PrimitiveOrStringType : BYTE
+        """
+        p[0] = IDLBuiltinType.Types.byte
+
+    def p_PrimitiveOrStringTypeOctet(self, p):
+        """
+            PrimitiveOrStringType : OCTET
+        """
+        p[0] = IDLBuiltinType.Types.octet
+
+    def p_PrimitiveOrStringTypeFloat(self, p):
+        """
+            PrimitiveOrStringType : FLOAT
+        """
+        p[0] = IDLBuiltinType.Types.float
+
+    def p_PrimitiveOrStringTypeUnrestictedFloat(self, p):
+        """
+            PrimitiveOrStringType : UNRESTRICTED FLOAT
+        """
+        p[0] = IDLBuiltinType.Types.unrestricted_float
+
+    def p_PrimitiveOrStringTypeDouble(self, p):
+        """
+            PrimitiveOrStringType : DOUBLE
+        """
+        p[0] = IDLBuiltinType.Types.double
+
+    def p_PrimitiveOrStringTypeUnrestictedDouble(self, p):
+        """
+            PrimitiveOrStringType : UNRESTRICTED DOUBLE
+        """
+        p[0] = IDLBuiltinType.Types.unrestricted_double
+
+    def p_PrimitiveOrStringTypeDOMString(self, p):
+        """
+            PrimitiveOrStringType : DOMSTRING
+        """
+        p[0] = IDLBuiltinType.Types.domstring
+
+    def p_PrimitiveOrStringTypeBytestring(self, p):
+        """
+            PrimitiveOrStringType : BYTESTRING
+        """
+        p[0] = IDLBuiltinType.Types.bytestring
+
+    def p_PrimitiveOrStringTypeUSVString(self, p):
+        """
+            PrimitiveOrStringType : USVSTRING
+        """
+        p[0] = IDLBuiltinType.Types.usvstring
+
+    def p_UnsignedIntegerTypeUnsigned(self, p):
+        """
+            UnsignedIntegerType : UNSIGNED IntegerType
+        """
+        # Adding one to a given signed integer type gets you the unsigned type:
+        p[0] = p[2] + 1
+
+    def p_UnsignedIntegerType(self, p):
+        """
+            UnsignedIntegerType : IntegerType
+        """
+        p[0] = p[1]
+
+    def p_IntegerTypeShort(self, p):
+        """
+            IntegerType : SHORT
+        """
+        p[0] = IDLBuiltinType.Types.short
+
+    def p_IntegerTypeLong(self, p):
+        """
+            IntegerType : LONG OptionalLong
+        """
+        if p[2]:
+            p[0] = IDLBuiltinType.Types.long_long
+        else:
+            p[0] = IDLBuiltinType.Types.long
+
+    def p_OptionalLong(self, p):
+        """
+            OptionalLong : LONG
+        """
+        p[0] = True
+
+    def p_OptionalLongEmpty(self, p):
+        """
+            OptionalLong :
+        """
+        p[0] = False
+
+    def p_Null(self, p):
+        """
+            Null : QUESTIONMARK
+                 |
+        """
+        if len(p) > 1:
+            p[0] = self.getLocation(p, 1)
+        else:
+            p[0] = None
+
+    def p_ReturnTypeType(self, p):
+        """
+            ReturnType : Type
+        """
+        p[0] = p[1]
+
+    def p_ReturnTypeVoid(self, p):
+        """
+            ReturnType : VOID
+        """
+        p[0] = BuiltinTypes[IDLBuiltinType.Types.void]
+
+    def p_ScopedName(self, p):
+        """
+            ScopedName : AbsoluteScopedName
+                       | RelativeScopedName
+        """
+        p[0] = p[1]
+
+    def p_AbsoluteScopedName(self, p):
+        """
+            AbsoluteScopedName : SCOPE IDENTIFIER ScopedNameParts
+        """
+        assert False
+        pass
+
+    def p_RelativeScopedName(self, p):
+        """
+            RelativeScopedName : IDENTIFIER ScopedNameParts
+        """
+        assert not p[2]  # Not implemented!
+
+        p[0] = IDLUnresolvedIdentifier(self.getLocation(p, 1), p[1])
+
+    def p_ScopedNameParts(self, p):
+        """
+            ScopedNameParts : SCOPE IDENTIFIER ScopedNameParts
+        """
+        assert False
+        pass
+
+    def p_ScopedNamePartsEmpty(self, p):
+        """
+            ScopedNameParts :
+        """
+        p[0] = None
+
+    def p_ExtendedAttributeNoArgs(self, p):
+        """
+            ExtendedAttributeNoArgs : IDENTIFIER
+        """
+        p[0] = (p[1],)
+
+    def p_ExtendedAttributeArgList(self, p):
+        """
+            ExtendedAttributeArgList : IDENTIFIER LPAREN ArgumentList RPAREN
+        """
+        p[0] = (p[1], p[3])
+
+    def p_ExtendedAttributeIdent(self, p):
+        """
+            ExtendedAttributeIdent : IDENTIFIER EQUALS STRING
+                                   | IDENTIFIER EQUALS IDENTIFIER
+        """
+        p[0] = (p[1], p[3])
+
+    def p_ExtendedAttributeNamedArgList(self, p):
+        """
+            ExtendedAttributeNamedArgList : IDENTIFIER EQUALS IDENTIFIER LPAREN ArgumentList RPAREN
+        """
+        p[0] = (p[1], p[3], p[5])
+
+    def p_ExtendedAttributeIdentList(self, p):
+        """
+            ExtendedAttributeIdentList : IDENTIFIER EQUALS LPAREN IdentifierList RPAREN
+        """
+        p[0] = (p[1], p[4])
+
+    def p_IdentifierList(self, p):
+        """
+            IdentifierList : IDENTIFIER Identifiers
+        """
+        idents = list(p[2])
+        idents.insert(0, p[1])
+        p[0] = idents
+
+    def p_IdentifiersList(self, p):
+        """
+            Identifiers : COMMA IDENTIFIER Identifiers
+        """
+        idents = list(p[3])
+        idents.insert(0, p[2])
+        p[0] = idents
+
+    def p_IdentifiersEmpty(self, p):
+        """
+            Identifiers :
+        """
+        p[0] = []
+
+    def p_error(self, p):
+        if not p:
+            raise WebIDLError("Syntax Error at end of file. Possibly due to missing semicolon(;), braces(}) or both",
+                              [self._filename])
+        else:
+            raise WebIDLError("invalid syntax", [Location(self.lexer, p.lineno, p.lexpos, self._filename)])
+
+    def __init__(self, outputdir='', lexer=None):
+        Tokenizer.__init__(self, outputdir, lexer)
+
+        logger = SqueakyCleanLogger()
+        try:
+            self.parser = yacc.yacc(module=self,
+                                    outputdir=outputdir,
+                                    tabmodule='webidlyacc',
+                                    errorlog=logger
+                                    # Pickling the grammar is a speedup in
+                                    # some cases (older Python?) but a
+                                    # significant slowdown in others.
+                                    # We're not pickling for now, until it
+                                    # becomes a speedup again.
+                                    # , picklefile='WebIDLGrammar.pkl'
+            )
+        finally:
+            logger.reportGrammarErrors()
+
+        self._globalScope = IDLScope(BuiltinLocation("<Global Scope>"), None, None)
+        # To make our test harness work, pretend like we have a primary global already.
+        # Note that we _don't_ set _globalScope.primaryGlobalAttr,
+        # so we'll still be able to detect multiple PrimaryGlobal extended attributes.
+        self._globalScope.primaryGlobalName = "FakeTestPrimaryGlobal"
+        self._globalScope.globalNames.add("FakeTestPrimaryGlobal")
+        self._globalScope.globalNameMapping["FakeTestPrimaryGlobal"].add("FakeTestPrimaryGlobal")
+        # And we add the special-cased "System" global name, which
+        # doesn't have any corresponding interfaces.
+        self._globalScope.globalNames.add("System")
+        self._globalScope.globalNameMapping["System"].add("BackstagePass")
+        self._installBuiltins(self._globalScope)
+        self._productions = []
+
+        self._filename = "<builtin>"
+        self.lexer.input(Parser._builtins)
+        self._filename = None
+
+        self.parser.parse(lexer=self.lexer, tracking=True)
+
+    def _installBuiltins(self, scope):
+        assert isinstance(scope, IDLScope)
+
+        # xrange omits the last value.
+        for x in xrange(IDLBuiltinType.Types.ArrayBuffer, IDLBuiltinType.Types.Float64Array + 1):
+            builtin = BuiltinTypes[x]
+            name = builtin.name
+            typedef = IDLTypedef(BuiltinLocation("<builtin type>"), scope, builtin, name)
+
+    @ staticmethod
+    def handleNullable(type, questionMarkLocation):
+        if questionMarkLocation is not None:
+            type = IDLNullableType(questionMarkLocation, type)
+
+        return type
+
+    def parse(self, t, filename=None):
+        self.lexer.input(t)
+
+        # for tok in iter(self.lexer.token, None):
+        #    print tok
+
+        self._filename = filename
+        self._productions.extend(self.parser.parse(lexer=self.lexer, tracking=True))
+        self._filename = None
+
+    def finish(self):
+        # If we have interfaces that are iterable, create their
+        # iterator interfaces and add them to the productions array.
+        interfaceStatements = []
+        for p in self._productions:
+            if isinstance(p, IDLInterface):
+                interfaceStatements.append(p)
+                if p.identifier.name == "Navigator":
+                    navigatorInterface = p
+
+        iterableIteratorIface = None
+        for iface in interfaceStatements:
+            navigatorProperty = iface.getNavigatorProperty()
+            if navigatorProperty:
+                # We're generating a partial interface to add a readonly
+                # property to the Navigator interface for every interface
+                # annotated with NavigatorProperty.
+                partialInterface = IDLPartialInterfaceOrNamespace(
+                    iface.location,
+                    IDLUnresolvedIdentifier(iface.location, "Navigator"),
+                    [ navigatorProperty ],
+                    navigatorInterface)
+                self._productions.append(partialInterface)
+
+            iterable = None
+            # We haven't run finish() on the interface yet, so we don't know
+            # whether our interface is maplike/setlike/iterable or not. This
+            # means we have to loop through the members to see if we have an
+            # iterable member.
+            for m in iface.members:
+                if isinstance(m, IDLIterable):
+                    iterable = m
+                    break
+            if iterable and iterable.isPairIterator():
+                def simpleExtendedAttr(str):
+                    return IDLExtendedAttribute(iface.location, (str, ))
+                nextMethod = IDLMethod(
+                    iface.location,
+                    IDLUnresolvedIdentifier(iface.location, "next"),
+                    BuiltinTypes[IDLBuiltinType.Types.object], [])
+                nextMethod.addExtendedAttributes([simpleExtendedAttr("Throws")])
+                itr_ident = IDLUnresolvedIdentifier(iface.location,
+                                                    iface.identifier.name + "Iterator")
+                itr_iface = IDLInterface(iface.location, self.globalScope(),
+                                         itr_ident, None, [nextMethod],
+                                         isKnownNonPartial=True)
+                itr_iface.addExtendedAttributes([simpleExtendedAttr("NoInterfaceObject")])
+                # Make sure the exposure set for the iterator interface is the
+                # same as the exposure set for the iterable interface, because
+                # we're going to generate methods on the iterable that return
+                # instances of the iterator.
+                itr_iface._exposureGlobalNames = set(iface._exposureGlobalNames)
+                # Always append generated iterable interfaces after the
+                # interface they're a member of, otherwise nativeType generation
+                # won't work correctly.
+                itr_iface.iterableInterface = iface
+                self._productions.append(itr_iface)
+                iterable.iteratorType = IDLWrapperType(iface.location, itr_iface)
+
+        # Then, finish all the IDLImplementsStatements.  In particular, we
+        # have to make sure we do those before we do the IDLInterfaces.
+        # XXX khuey hates this bit and wants to nuke it from orbit.
+        implementsStatements = [p for p in self._productions if
+                                isinstance(p, IDLImplementsStatement)]
+        otherStatements = [p for p in self._productions if
+                           not isinstance(p, IDLImplementsStatement)]
+        for production in implementsStatements:
+            production.finish(self.globalScope())
+        for production in otherStatements:
+            production.finish(self.globalScope())
+
+        # Do any post-finish validation we need to do
+        for production in self._productions:
+            production.validate()
+
+        # De-duplicate self._productions, without modifying its order.
+        seen = set()
+        result = []
+        for p in self._productions:
+            if p not in seen:
+                seen.add(p)
+                result.append(p)
+        return result
+
+    def reset(self):
+        return Parser(lexer=self.lexer)
+
+    # Builtin IDL defined by WebIDL
+    _builtins = """
+        typedef unsigned long long DOMTimeStamp;
+        typedef (ArrayBufferView or ArrayBuffer) BufferSource;
+    """
+
+
+def main():
+    # Parse arguments.
+    from optparse import OptionParser
+    usageString = "usage: %prog [options] files"
+    o = OptionParser(usage=usageString)
+    o.add_option("--cachedir", dest='cachedir', default=None,
+                 help="Directory in which to cache lex/parse tables.")
+    o.add_option("--verbose-errors", action='store_true', default=False,
+                 help="When an error happens, display the Python traceback.")
+    (options, args) = o.parse_args()
+
+    if len(args) < 1:
+        o.error(usageString)
+
+    fileList = args
+    baseDir = os.getcwd()
+
+    # Parse the WebIDL.
+    parser = Parser(options.cachedir)
+    try:
+        for filename in fileList:
+            fullPath = os.path.normpath(os.path.join(baseDir, filename))
+            f = open(fullPath, 'rb')
+            lines = f.readlines()
+            f.close()
+            print fullPath
+            parser.parse(''.join(lines), fullPath)
+        parser.finish()
+    except WebIDLError, e:
+        if options.verbose_errors:
+            traceback.print_exc()
+        else:
+            print e
+
+if __name__ == '__main__':
+    main()