--- a/dom/bindings/Bindings.conf
+++ b/dom/bindings/Bindings.conf
@@ -494,16 +494,17 @@ DOMInterfaces = {
     'implicitJSContext': [ 'constructor' ]
 }],
 
 ####################################
 # Test Interfaces of various sorts #
 ####################################
 
 'TestInterface' : {
+        # Keep this in sync with TestExampleInterface
         'headerFile': 'TestBindingHeader.h',
         'register': False,
         'resultNotAddRefed': [ 'receiveWeakSelf', 'receiveWeakNullableSelf',
                                'receiveWeakOther', 'receiveWeakNullableOther',
                                'receiveWeakExternal', 'receiveWeakNullableExternal',
                                'ReceiveWeakCallbackInterface',
                                'ReceiveWeakNullableCallbackInterface',
                                'receiveWeakCastableObjectSequence',
@@ -582,16 +583,34 @@ DOMInterfaces = {
         'register': False
         },
 
 'TestIndexedAndNamedGetterAndSetterInterface' : {
         'headerFile': 'TestBindingHeader.h',
         'register': False,
         'binaryNames': { '__stringifier': 'Stringify' }
         },
+
+'TestExampleInterface' : {
+        # Keep this in sync with TestInterface
+        'headerFile': 'TestExampleInterface-example.h',
+        'register': False,
+        'resultNotAddRefed': [ 'receiveWeakSelf', 'receiveWeakNullableSelf',
+                               'receiveWeakOther', 'receiveWeakNullableOther',
+                               'receiveWeakExternal', 'receiveWeakNullableExternal',
+                               'ReceiveWeakCallbackInterface',
+                               'ReceiveWeakNullableCallbackInterface',
+                               'receiveWeakCastableObjectSequence',
+                               'receiveWeakNullableCastableObjectSequence',
+                               'receiveWeakCastableObjectNullableSequence',
+                               'receiveWeakNullableCastableObjectNullableSequence' ],
+        'binaryNames': { 'methodRenamedFrom': 'methodRenamedTo',
+                         'attributeGetterRenamedFrom': 'attributeGetterRenamedTo',
+                         'attributeRenamedFrom': 'attributeRenamedTo' }
+        }
 }
 
 # These are temporary, until they've been converted to use new DOM bindings
 def addExternalIface(iface, nativeType=None, headerFile=None):
     if iface in DOMInterfaces:
         raise Exception('Interface declared both as WebIDL and External interface')
     domInterface = {
         'concrete': False

--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -5959,31 +5959,40 @@ class CGExampleMember(CGThing):
                     typeDecl = "%s&"
             return (typeDecl % iface.identifier.name), False, False
 
         if type.isSpiderMonkeyInterface():
             assert not isMember
             if type.nullable():
                 typeDecl = "%s*"
             else:
-                typeDecl = "%s&"
+                typeDecl = "%s"
+                if not optional:
+                    typeDecl += "&"
             return (typeDecl % type.name), False, False
 
         if type.isString():
             if isMember:
                 declType = "nsString"
             else:
                 declType = "nsAString"
             return declType, True, False
 
         if type.isEnum():
             return type.inner.identifier.name, False, True
 
         if type.isCallback():
-            return "JSObject*", False, False
+            if type.nullable():
+                declType = "JSObject*"
+            else:
+                if optional:
+                    declType = "NonNull<JSObject>"
+                else:
+                    declType = "JSObject&"
+            return declType, False, False
 
         if type.isAny():
             return "JS::Value", False, False
 
         if type.isObject():
             if type.nullable():
                 declType = "%s*"
             else:
@@ -6092,21 +6101,18 @@ class CGExampleClass(CGThing):
                     "{\n"
                     "public:\n"
                     "  ${ifaceName}();\n"
                     "  ~${ifaceName}();\n"
                     "\n"
                     "  NS_DECL_CYCLE_COLLECTING_ISUPPORTS\n"
                     "  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(${ifaceName})\n"
                     "\n"
-                    "  void* GetParentObject() const\n"
-                    "  {\n"
-                    "    // TODO: return something sensible here, and change the return type\n"
-                    "    return somethingSensible;\n"
-                    "  }\n"
+                    "  // TODO: return something sensible here, and change the return type\n"
+                    "  ${ifaceName}* GetParentObject() const;\n"
                     "\n" +
                     wrapFunc +
                     "\n").substitute({ "ifaceName": descriptor.name })),
             reindent=True)
 
         self.decl = CGWrapper(self.decl,
                               pre=("\n" + classDecl.define()),
                               post="\n};\n\n")

--- a/dom/bindings/test/Makefile.in
+++ b/dom/bindings/test/Makefile.in
@@ -70,19 +70,23 @@ MOCHITEST_CHROME_FILES = \
   $(NULL)
 
 # Include rules.mk before any of our targets so our first target is coming from
 # rules.mk and running make with no target in this dir does the right thing.
 include $(topsrcdir)/config/rules.mk
 
 $(CPPSRCS): ../%Binding.cpp: $(bindinggen_dependencies) \
                              ../%.webidl \
+                             TestExampleInterface-example \
                              $(NULL)
 	$(MAKE) -C .. $*Binding.h
 	$(MAKE) -C .. $*Binding.cpp
 
+TestExampleInterface-example:
+	$(MAKE) -C .. TestExampleInterface-example
+
 check::
 	PYTHONDONTWRITEBYTECODE=1 $(PYTHON) $(topsrcdir)/config/pythonpath.py \
 	  $(PLY_INCLUDE) $(srcdir)/../parser/runtests.py
 
 check-interactive:
 	PYTHONDONTWRITEBYTECODE=1 $(PYTHON) $(topsrcdir)/config/pythonpath.py \
 	  $(PLY_INCLUDE) $(srcdir)/../parser/runtests.py -q

--- a/dom/bindings/test/TestCodeGen.webidl
+++ b/dom/bindings/test/TestCodeGen.webidl
@@ -29,17 +29,17 @@ callback TestCallback = void();
 TestInterface implements ImplementedInterface;
 
 // This interface is only for use in the constructor below
 interface OnlyForUseInConstructor {
 };
 
 [Constructor,
  Constructor(DOMString str),
- Constructor(unsigned long num, boolean? bool),
+ Constructor(unsigned long num, boolean? boolArg),
  Constructor(TestInterface? iface),
  Constructor(TestNonCastableInterface iface)
  // , Constructor(long arg1, long arg2, (TestInterface or OnlyForUseInConstructor) arg3)
  ]
 interface TestInterface {
   // Integer types
   // XXXbz add tests for throwing versions of all the integer stuff
   readonly attribute byte readonlyByte;
@@ -327,16 +327,18 @@ interface TestInterface {
   // Typedefs
   const myLong myLongConstant = 5;
   void exerciseTypedefInterfaces1(AnotherNameForTestInterface arg);
   AnotherNameForTestInterface exerciseTypedefInterfaces2(NullableTestInterface arg);
   void exerciseTypedefInterfaces3(YetAnotherNameForTestInterface arg);
 
   // Miscellania
   [LenientThis] attribute long attrWithLenientThis;
+
+  // If you add things here, add them to TestExampleGen as well
 };
 
 interface TestNonWrapperCacheInterface {
 };
 
 interface ImplementedInterfaceParent {
   void implementedParentMethod();
   attribute boolean implementedParentProperty;

new file mode 100644
--- /dev/null
+++ b/dom/bindings/test/TestExampleGen.webidl
@@ -0,0 +1,308 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/.
+ */
+[Constructor,
+ Constructor(DOMString str),
+ Constructor(unsigned long num, boolean? boolArg),
+ Constructor(TestInterface? iface),
+ Constructor(TestNonCastableInterface iface)
+ // , Constructor(long arg1, long arg2, (TestInterface or OnlyForUseInConstructor) arg3)
+ ]
+interface TestExampleInterface {
+  // Integer types
+  // XXXbz add tests for throwing versions of all the integer stuff
+  readonly attribute byte readonlyByte;
+  attribute byte writableByte;
+  void passByte(byte arg);
+  byte receiveByte();
+  void passOptionalByte(optional byte arg);
+  void passOptionalByteWithDefault(optional byte arg = 0);
+  void passNullableByte(byte? arg);
+  void passOptionalNullableByte(optional byte? arg);
+
+  readonly attribute short readonlyShort;
+  attribute short writableShort;
+  void passShort(short arg);
+  short receiveShort();
+  void passOptionalShort(optional short arg);
+  void passOptionalShortWithDefault(optional short arg = 5);
+
+  readonly attribute long readonlyLong;
+  attribute long writableLong;
+  void passLong(long arg);
+  long receiveLong();
+  void passOptionalLong(optional long arg);
+  void passOptionalLongWithDefault(optional long arg = 7);
+
+  readonly attribute long long readonlyLongLong;
+  attribute long long writableLongLong;
+  void passLongLong(long long arg);
+  long long receiveLongLong();
+  void passOptionalLongLong(optional long long arg);
+  void passOptionalLongLongWithDefault(optional long long arg = -12);
+
+  readonly attribute octet readonlyOctet;
+  attribute octet writableOctet;
+  void passOctet(octet arg);
+  octet receiveOctet();
+  void passOptionalOctet(optional octet arg);
+  void passOptionalOctetWithDefault(optional octet arg = 19);
+
+  readonly attribute unsigned short readonlyUnsignedShort;
+  attribute unsigned short writableUnsignedShort;
+  void passUnsignedShort(unsigned short arg);
+  unsigned short receiveUnsignedShort();
+  void passOptionalUnsignedShort(optional unsigned short arg);
+  void passOptionalUnsignedShortWithDefault(optional unsigned short arg = 2);
+
+  readonly attribute unsigned long readonlyUnsignedLong;
+  attribute unsigned long writableUnsignedLong;
+  void passUnsignedLong(unsigned long arg);
+  unsigned long receiveUnsignedLong();
+  void passOptionalUnsignedLong(optional unsigned long arg);
+  void passOptionalUnsignedLongWithDefault(optional unsigned long arg = 6);
+
+  readonly attribute unsigned long long readonlyUnsignedLongLong;
+  attribute unsigned long long  writableUnsignedLongLong;
+  void passUnsignedLongLong(unsigned long long arg);
+  unsigned long long receiveUnsignedLongLong();
+  void passOptionalUnsignedLongLong(optional unsigned long long arg);
+  void passOptionalUnsignedLongLongWithDefault(optional unsigned long long arg = 17);
+
+  // Castable interface types
+  // XXXbz add tests for throwing versions of all the castable interface stuff
+  TestInterface receiveSelf();
+  TestInterface? receiveNullableSelf();
+  TestInterface receiveWeakSelf();
+  TestInterface? receiveWeakNullableSelf();
+  // A verstion to test for casting to TestInterface&
+  void passSelf(TestInterface arg);
+  // A version we can use to test for the exact type passed in
+  void passSelf2(TestInterface arg);
+  void passNullableSelf(TestInterface? arg);
+  attribute TestInterface nonNullSelf;
+  attribute TestInterface? nullableSelf;
+  // Optional arguments
+  void passOptionalSelf(optional TestInterface? arg);
+  void passOptionalNonNullSelf(optional TestInterface arg);
+  void passOptionalSelfWithDefault(optional TestInterface? arg = null);
+
+  // Non-wrapper-cache interface types
+  [Creator]
+  TestNonWrapperCacheInterface receiveNonWrapperCacheInterface();
+  [Creator]
+  TestNonWrapperCacheInterface? receiveNullableNonWrapperCacheInterface();
+  [Creator]
+  sequence<TestNonWrapperCacheInterface> receiveNonWrapperCacheInterfaceSequence();
+  [Creator]
+  sequence<TestNonWrapperCacheInterface?> receiveNullableNonWrapperCacheInterfaceSequence();
+  [Creator]
+  sequence<TestNonWrapperCacheInterface>? receiveNonWrapperCacheInterfaceNullableSequence();
+  [Creator]
+  sequence<TestNonWrapperCacheInterface?>? receiveNullableNonWrapperCacheInterfaceNullableSequence();
+
+  // Non-castable interface types
+  TestNonCastableInterface receiveOther();
+  TestNonCastableInterface? receiveNullableOther();
+  TestNonCastableInterface receiveWeakOther();
+  TestNonCastableInterface? receiveWeakNullableOther();
+  // A verstion to test for casting to TestNonCastableInterface&
+  void passOther(TestNonCastableInterface arg);
+  // A version we can use to test for the exact type passed in
+  void passOther2(TestNonCastableInterface arg);
+  void passNullableOther(TestNonCastableInterface? arg);
+  attribute TestNonCastableInterface nonNullOther;
+  attribute TestNonCastableInterface? nullableOther;
+  // Optional arguments
+  void passOptionalOther(optional TestNonCastableInterface? arg);
+  void passOptionalNonNullOther(optional TestNonCastableInterface arg);
+  void passOptionalOtherWithDefault(optional TestNonCastableInterface? arg = null);
+
+  // External interface types
+  TestExternalInterface receiveExternal();
+  TestExternalInterface? receiveNullableExternal();
+  TestExternalInterface receiveWeakExternal();
+  TestExternalInterface? receiveWeakNullableExternal();
+  // A verstion to test for casting to TestExternalInterface&
+  void passExternal(TestExternalInterface arg);
+  // A version we can use to test for the exact type passed in
+  void passExternal2(TestExternalInterface arg);
+  void passNullableExternal(TestExternalInterface? arg);
+  attribute TestExternalInterface nonNullExternal;
+  attribute TestExternalInterface? nullableExternal;
+  // Optional arguments
+  void passOptionalExternal(optional TestExternalInterface? arg);
+  void passOptionalNonNullExternal(optional TestExternalInterface arg);
+  void passOptionalExternalWithDefault(optional TestExternalInterface? arg = null);
+
+  // Callback interface types
+  TestCallbackInterface receiveCallbackInterface();
+  TestCallbackInterface? receiveNullableCallbackInterface();
+  TestCallbackInterface receiveWeakCallbackInterface();
+  TestCallbackInterface? receiveWeakNullableCallbackInterface();
+  // A verstion to test for casting to TestCallbackInterface&
+  void passCallbackInterface(TestCallbackInterface arg);
+  // A version we can use to test for the exact type passed in
+  void passCallbackInterface2(TestCallbackInterface arg);
+  void passNullableCallbackInterface(TestCallbackInterface? arg);
+  attribute TestCallbackInterface nonNullCallbackInterface;
+  attribute TestCallbackInterface? nullableCallbackInterface;
+  // Optional arguments
+  void passOptionalCallbackInterface(optional TestCallbackInterface? arg);
+  void passOptionalNonNullCallbackInterface(optional TestCallbackInterface arg);
+  void passOptionalCallbackInterfaceWithDefault(optional TestCallbackInterface? arg = null);
+
+  // Miscellaneous interface tests
+  IndirectlyImplementedInterface receiveConsequentialInterface();
+  void passConsequentialInterface(IndirectlyImplementedInterface arg);
+
+  // Sequence types
+  sequence<long> receiveSequence();
+  sequence<long>? receiveNullableSequence();
+  sequence<long?> receiveSequenceOfNullableInts();
+  sequence<long?>? receiveNullableSequenceOfNullableInts();
+  void passSequence(sequence<long> arg);
+  void passNullableSequence(sequence<long>? arg);
+  void passSequenceOfNullableInts(sequence<long?> arg);
+  void passOptionalSequenceOfNullableInts(optional sequence<long?> arg);
+  void passOptionalNullableSequenceOfNullableInts(optional sequence<long?>? arg);
+  sequence<TestInterface> receiveCastableObjectSequence();
+  sequence<TestCallbackInterface> receiveCallbackObjectSequence();
+  sequence<TestInterface?> receiveNullableCastableObjectSequence();
+  sequence<TestCallbackInterface?> receiveNullableCallbackObjectSequence();
+  sequence<TestInterface>? receiveCastableObjectNullableSequence();
+  sequence<TestInterface?>? receiveNullableCastableObjectNullableSequence();
+  sequence<TestInterface> receiveWeakCastableObjectSequence();
+  sequence<TestInterface?> receiveWeakNullableCastableObjectSequence();
+  sequence<TestInterface>? receiveWeakCastableObjectNullableSequence();
+  sequence<TestInterface?>? receiveWeakNullableCastableObjectNullableSequence();
+  void passCastableObjectSequence(sequence<TestInterface> arg);
+  void passNullableCastableObjectSequence(sequence<TestInterface?> arg);
+  void passCastableObjectNullableSequence(sequence<TestInterface>? arg);
+  void passNullableCastableObjectNullableSequence(sequence<TestInterface?>? arg);
+  void passOptionalSequence(optional sequence<long> arg);
+  void passOptionalNullableSequence(optional sequence<long>? arg);
+  void passOptionalNullableSequenceWithDefaultValue(optional sequence<long>? arg = null);
+  void passOptionalObjectSequence(optional sequence<TestInterface> arg);
+
+  sequence<DOMString> receiveStringSequence();
+  void passStringSequence(sequence<DOMString> arg);
+
+  sequence<any> receiveAnySequence();
+  sequence<any>? receiveNullableAnySequence();
+
+  // Typed array types
+  void passArrayBuffer(ArrayBuffer arg);
+  void passNullableArrayBuffer(ArrayBuffer? arg);
+  void passOptionalArrayBuffer(optional ArrayBuffer arg);
+  void passOptionalNullableArrayBuffer(optional ArrayBuffer? arg);
+  void passOptionalNullableArrayBufferWithDefaultValue(optional ArrayBuffer? arg= null);
+  void passArrayBufferView(ArrayBufferView arg);
+  void passInt8Array(Int8Array arg);
+  void passInt16Array(Int16Array arg);
+  void passInt32Array(Int32Array arg);
+  void passUint8Array(Uint8Array arg);
+  void passUint16Array(Uint16Array arg);
+  void passUint32Array(Uint32Array arg);
+  void passUint8ClampedArray(Uint8ClampedArray arg);
+  void passFloat32Array(Float32Array arg);
+  void passFloat64Array(Float64Array arg);
+  Uint8Array receiveUint8Array();
+
+  // String types
+  void passString(DOMString arg);
+  void passNullableString(DOMString? arg);
+  void passOptionalString(optional DOMString arg);
+  void passOptionalStringWithDefaultValue(optional DOMString arg = "abc");
+  void passOptionalNullableString(optional DOMString? arg);
+  void passOptionalNullableStringWithDefaultValue(optional DOMString? arg = null);
+
+  // Enumerated types
+  void passEnum(TestEnum arg);
+  // No support for nullable enums yet
+  // void passNullableEnum(TestEnum? arg);
+  void passOptionalEnum(optional TestEnum arg);
+  void passEnumWithDefault(optional TestEnum arg = "a");
+  // void passOptionalNullableEnum(optional TestEnum? arg);
+  // void passOptionalNullableEnumWithDefaultValue(optional TestEnum? arg = null);
+  TestEnum receiveEnum();
+  attribute TestEnum enumAttribute;
+  readonly attribute TestEnum readonlyEnumAttribute;
+
+  // Callback types
+  void passCallback(TestCallback arg);
+  void passNullableCallback(TestCallback? arg);
+  void passOptionalCallback(optional TestCallback arg);
+  void passOptionalNullableCallback(optional TestCallback? arg);
+  void passOptionalNullableCallbackWithDefaultValue(optional TestCallback? arg = null);
+  TestCallback receiveCallback();
+  TestCallback? receiveNullableCallback();
+  void passNullableTreatAsNullCallback(TestTreatAsNullCallback? arg);
+  void passOptionalNullableTreatAsNullCallback(optional TestTreatAsNullCallback? arg);
+  void passOptionalNullableTreatAsNullCallbackWithDefaultValue(optional TestTreatAsNullCallback? arg = null);
+
+  // Any types
+  void passAny(any arg);
+  void passOptionalAny(optional any arg);
+  void passAnyDefaultNull(optional any arg = null);
+  any receiveAny();
+
+  // object types
+  void passObject(object arg);
+  void passNullableObject(object? arg);
+  void passOptionalObject(optional object arg);
+  void passOptionalNullableObject(optional object? arg);
+  void passOptionalNullableObjectWithDefaultValue(optional object? arg = null);
+  object receiveObject();
+  object? receiveNullableObject();
+
+  // Union types
+  void passUnion((object or long) arg);
+  void passUnionWithNullable((object? or long) arg);
+  void passNullableUnion((object or long)? arg);
+  void passOptionalUnion(optional (object or long) arg);
+  void passOptionalNullableUnion(optional (object or long)? arg);
+  void passOptionalNullableUnionWithDefaultValue(optional (object or long)? arg = null);
+  //void passUnionWithInterfaces((TestInterface or TestExternalInterface) arg);
+  //void passUnionWithInterfacesAndNullable((TestInterface? or TestExternalInterface) arg);
+  //void passUnionWithSequence((sequence<object> or long) arg);
+  void passUnionWithArrayBuffer((ArrayBuffer or long) arg);
+  void passUnionWithString((DOMString or object) arg);
+  //void passUnionWithEnum((TestEnum or object) arg);
+  void passUnionWithCallback((TestCallback or long) arg);
+  void passUnionWithObject((object or long) arg);
+  //void passUnionWithDict((Dict or long) arg);
+
+  // binaryNames tests
+  void methodRenamedFrom();
+  void methodRenamedFrom(byte argument);
+  readonly attribute byte attributeGetterRenamedFrom;
+  attribute byte attributeRenamedFrom;
+
+  void passDictionary(optional Dict x);
+  void passOtherDictionary(optional GrandparentDict x);
+  void passSequenceOfDictionaries(sequence<Dict> x);
+  void passDictionaryOrLong(optional Dict x);
+  void passDictionaryOrLong(long x);
+
+  void passDictContainingDict(optional DictContainingDict arg);
+  void passDictContainingSequence(optional DictContainingSequence arg);
+
+  // EnforceRange/Clamp tests
+  void dontEnforceRangeOrClamp(byte arg);
+  void doEnforceRange([EnforceRange] byte arg);
+  void doClamp([Clamp] byte arg);
+
+  // Typedefs
+  const myLong myLongConstant = 5;
+  void exerciseTypedefInterfaces1(AnotherNameForTestInterface arg);
+  AnotherNameForTestInterface exerciseTypedefInterfaces2(NullableTestInterface arg);
+  void exerciseTypedefInterfaces3(YetAnotherNameForTestInterface arg);
+
+  // Miscellania
+  [LenientThis] attribute long attrWithLenientThis;
+
+  // If you add things here, add them to TestCodeGen as well
+};

--- a/dom/webidl/WebIDL.mk
+++ b/dom/webidl/WebIDL.mk
@@ -66,14 +66,15 @@ webidl_files += \
   USSDReceivedEvent.webidl \
   $(NULL)
 endif
 
 ifdef ENABLE_TESTS
 test_webidl_files := \
   TestCodeGen.webidl \
   TestDictionary.webidl \
+  TestExampleGen.webidl \
   TestTypedef.webidl \
   $(NULL)
 else
 test_webidl_files := $(NULL)
 endif