IDL: Improve "argument needs v8::TryCatch" logic slightly

Source/bindings/scripts/v8_methods.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 34 matching lines @@
 # Methods with any of these require custom method registration code in the
 # interface's configure*Template() function.
 CUSTOM_REGISTRATION_EXTENDED_ATTRIBUTES = frozenset([
     'DoNotCheckSecurity',
     'DoNotCheckSignature',
     'NotEnumerable',
     'Unforgeable',
 ])
 
 
-def argument_needs_try_catch(argument, return_promise):
+def argument_needs_try_catch(method, argument):
+    return_promise = method.idl_type and method.idl_type.name == 'Promise'
     idl_type = argument.idl_type
     base_type = idl_type.base_type
 
-    return not (
+    return not(
         # These cases are handled by separate code paths in the
         # generate_argument() macro in Source/bindings/templates/methods.cpp.
         idl_type.is_callback_interface or
         base_type == 'SerializedScriptValue' or
         (argument.is_variadic and idl_type.is_wrapper_type) or
         # String and enumeration arguments converted using one of the
         # TOSTRING_* macros except for _PROMISE variants in
         # Source/bindings/core/v8/V8BindingMacros.h don't use a v8::TryCatch.
-        (base_type == 'DOMString' and not argument.is_variadic and
+        ((base_type == 'DOMString' or idl_type.is_enum) and
+         not argument.is_variadic and
          not return_promise))
 
 
 def use_local_result(method):
     extended_attributes = method.extended_attributes
     idl_type = method.idl_type
     return (has_extended_attribute_value(method, 'CallWith', 'ScriptState') or
             'ImplementedInPrivateScript' in extended_attributes or
             'RaisesException' in extended_attributes or
             idl_type.is_union_type or
             idl_type.is_explicit_nullable)
 
 
 def method_context(interface, method):
     arguments = method.arguments
     extended_attributes = method.extended_attributes
     idl_type = method.idl_type
     is_static = method.is_static
     name = method.name
-    return_promise = idl_type.name == 'Promise'
 
     idl_type.add_includes_for_type()
     this_cpp_value = cpp_value(interface, method, len(arguments))
 
     def function_template():
         if is_static:
             return 'functionTemplate'
         if 'Unforgeable' in extended_attributes:
             return 'instanceTemplate'
         return 'prototypeTemplate'
@@ skipping 20 matching lines @@
     is_custom_element_callbacks = 'CustomElementCallbacks' in extended_attributes
     if is_custom_element_callbacks:
         includes.add('core/dom/custom/CustomElementCallbackDispatcher.h')
 
     is_check_security_for_frame = (
         'CheckSecurity' in interface.extended_attributes and
         'DoNotCheckSecurity' not in extended_attributes)
     is_raises_exception = 'RaisesException' in extended_attributes
 
     arguments_need_try_catch = (
-        any(argument_needs_try_catch(argument, return_promise)
+        any(argument_needs_try_catch(method, argument)
             for argument in arguments))
 
     return {
         'activity_logging_world_list': v8_utilities.activity_logging_world_list(method),  # [ActivityLogging]
         'arguments': [argument_context(interface, method, argument, index)
                       for index, argument in enumerate(arguments)],
         'argument_declarations_for_private_script':
             argument_declarations_for_private_script(interface, method),
         'arguments_need_try_catch': arguments_need_try_catch,
         'conditional_string': v8_utilities.conditional_string(method),
@@ skipping 297 matching lines @@
 
 
 def argument_default_cpp_value(argument):
     if not argument.default_value:
         return None
     return argument.idl_type.literal_cpp_value(argument.default_value)
 
 IdlTypeBase.union_arguments = None
 IdlUnionType.union_arguments = property(union_arguments)
 IdlArgument.default_cpp_value = property(argument_default_cpp_value)