Remove unused V8 integration code in Sky

sky/engine/bindings/scripts/v8_interface.py

-# Copyright (C) 2013 Google Inc. All rights reserved.
-# coding=utf-8
-#
-# 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
-# in the documentation and/or other materials provided with the
-# distribution.
-#     * Neither the name of Google Inc. nor the names of its
-# contributors may be used to endorse or promote products derived from
-# this software without specific prior written permission.
-#
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-
-"""Generate template values for an interface.
-
-Design doc: http://www.chromium.org/developers/design-documents/idl-compiler
-"""
-
-from collections import defaultdict
-import itertools
-from operator import itemgetter
-
-import idl_definitions
-from idl_definitions import IdlOperation
-import idl_types
-from idl_types import IdlType, inherits_interface
-import v8_attributes
-from v8_globals import includes
-import v8_methods
-import v8_types
-from v8_types import cpp_template_type
-import v8_utilities
-from v8_utilities import (capitalize, conditional_string, cpp_name,
-                          has_extended_attribute_value, runtime_enabled_function_name,
-                          extended_attribute_value_as_list)
-
-
-INTERFACE_H_INCLUDES = frozenset([
-    'bindings/core/v8/ScriptWrappable.h',
-    'bindings/core/v8/V8Binding.h',
-    'bindings/core/v8/V8DOMWrapper.h',
-    'bindings/core/v8/WrapperTypeInfo.h',
-    'platform/heap/Handle.h',
-])
-INTERFACE_CPP_INCLUDES = frozenset([
-    'bindings/core/v8/ExceptionState.h',
-    'bindings/core/v8/V8DOMConfiguration.h',
-    'bindings/core/v8/V8HiddenValue.h',
-    'bindings/core/v8/V8ObjectConstructor.h',
-    'core/dom/Document.h',
-    'platform/RuntimeEnabledFeatures.h',
-    'platform/TraceEvent.h',
-    'wtf/GetPtr.h',
-    'wtf/RefPtr.h',
-])
-
-
-def interface_context(interface):
-    includes.clear()
-    includes.update(INTERFACE_CPP_INCLUDES)
-    header_includes = set(INTERFACE_H_INCLUDES)
-
-    parent_interface = interface.parent
-    if parent_interface:
-        header_includes.update(v8_types.includes_for_interface(parent_interface))
-    extended_attributes = interface.extended_attributes
-
-    is_document = inherits_interface(interface.name, 'Document')
-    if is_document:
-        includes.update(['bindings/core/v8/ScriptController.h',
-                         'bindings/core/v8/WindowProxy.h',
-                         'core/frame/LocalFrame.h'])
-
-    # [ActiveDOMObject]
-    is_active_dom_object = 'ActiveDOMObject' in extended_attributes
-
-    # [CheckSecurity]
-    is_check_security = 'CheckSecurity' in extended_attributes
-    if is_check_security:
-        includes.add('bindings/core/v8/BindingSecurity.h')
-
-    # [DependentLifetime]
-    is_dependent_lifetime = 'DependentLifetime' in extended_attributes
-
-    # [Iterable]
-    iterator_method = None
-    if 'Iterable' in extended_attributes:
-        iterator_operation = IdlOperation(interface.idl_name)
-        iterator_operation.name = 'iterator'
-        iterator_operation.idl_type = IdlType('Iterator')
-        iterator_operation.extended_attributes['RaisesException'] = None
-        iterator_operation.extended_attributes['CallWith'] = 'ScriptState'
-        iterator_method = v8_methods.method_context(interface,
-                                                    iterator_operation)
-
-    # [MeasureAs]
-    is_measure_as = 'MeasureAs' in extended_attributes
-
-    # [SetWrapperReferenceFrom]
-    reachable_node_function = extended_attributes.get('SetWrapperReferenceFrom')
-    if reachable_node_function:
-        includes.update(['bindings/core/v8/V8GCController.h',
-                         'core/dom/Element.h'])
-
-    # [SetWrapperReferenceTo]
-    set_wrapper_reference_to_list = [{
-        'name': argument.name,
-        # FIXME: properly should be:
-        # 'cpp_type': argument.idl_type.cpp_type_args(raw_type=True),
-        # (if type is non-wrapper type like NodeFilter, normally RefPtr)
-        # Raw pointers faster though, and NodeFilter hacky anyway.
-        'cpp_type': argument.idl_type.implemented_as + '*',
-        'idl_type': argument.idl_type,
-        'v8_type': v8_types.v8_type(argument.idl_type.name),
-    } for argument in extended_attributes.get('SetWrapperReferenceTo', [])]
-    for set_wrapper_reference_to in set_wrapper_reference_to_list:
-        set_wrapper_reference_to['idl_type'].add_includes_for_type()
-
-    # [NotScriptWrappable]
-    is_script_wrappable = 'NotScriptWrappable' not in extended_attributes
-
-    # [SpecialWrapFor]
-    if 'SpecialWrapFor' in extended_attributes:
-        special_wrap_for = extended_attribute_value_as_list(interface, 'SpecialWrapFor')
-    else:
-        special_wrap_for = []
-    for special_wrap_interface in special_wrap_for:
-        v8_types.add_includes_for_interface(special_wrap_interface)
-
-    # [Custom=Wrap], [SetWrapperReferenceFrom]
-    has_visit_dom_wrapper = (
-        has_extended_attribute_value(interface, 'Custom', 'VisitDOMWrapper') or
-        reachable_node_function or
-        set_wrapper_reference_to_list)
-
-    wrapper_class_id = ('NodeClassId' if inherits_interface(interface.name, 'Node') else 'ObjectClassId')
-
-    context = {
-        'conditional_string': conditional_string(interface),  # [Conditional]
-        'cpp_class': cpp_name(interface),
-        # FIXME: Remove 'EventTarget' special handling, http://crbug.com/383699
-        'has_access_check_callbacks': (is_check_security and
-                                       interface.name != 'Window' and
-                                       interface.name != 'EventTarget'),
-        'has_custom_legacy_call_as_function': has_extended_attribute_value(interface, 'Custom', 'LegacyCallAsFunction'),  # [Custom=LegacyCallAsFunction]
-        'has_custom_to_v8': has_extended_attribute_value(interface, 'Custom', 'ToV8'),  # [Custom=ToV8]
-        'has_custom_wrap': has_extended_attribute_value(interface, 'Custom', 'Wrap'),  # [Custom=Wrap]
-        'has_visit_dom_wrapper': has_visit_dom_wrapper,
-        'header_includes': header_includes,
-        'interface_name': interface.name,
-        'is_active_dom_object': is_active_dom_object,
-        'is_check_security': is_check_security,
-        'is_dependent_lifetime': is_dependent_lifetime,
-        'is_document': is_document,
-        'is_event_target': inherits_interface(interface.name, 'EventTarget'),
-        'is_exception': interface.is_exception,
-        'is_node': inherits_interface(interface.name, 'Node'),
-        'is_script_wrappable': is_script_wrappable,
-        'iterator_method': iterator_method,
-        'lifetime': 'Dependent'
-            if (has_visit_dom_wrapper or
-                is_active_dom_object or
-                is_dependent_lifetime)
-            else 'Independent',
-        'measure_as': v8_utilities.measure_as(interface),  # [MeasureAs]
-        'parent_interface': parent_interface,
-        'pass_cpp_type': cpp_template_type(
-            'PassRefPtr',
-            cpp_name(interface)),
-        'reachable_node_function': reachable_node_function,
-        'runtime_enabled_function': runtime_enabled_function_name(interface),  # [RuntimeEnabled]
-        'set_wrapper_reference_to_list': set_wrapper_reference_to_list,
-        'special_wrap_for': special_wrap_for,
-        'v8_class': v8_utilities.v8_class_name(interface),
-        'wrapper_class_id': wrapper_class_id,
-    }
-
-    # Constructors
-    constructors = [constructor_context(interface, constructor)
-                    for constructor in interface.constructors
-                    # FIXME: shouldn't put named constructors with constructors
-                    # (currently needed for Perl compatibility)
-                    # Handle named constructors separately
-                    if constructor.name == 'Constructor']
-    if len(constructors) > 1:
-        context['constructor_overloads'] = overloads_context(constructors)
-
-    # [CustomConstructor]
-    custom_constructors = [{  # Only needed for computing interface length
-        'number_of_required_arguments':
-            number_of_required_arguments(constructor),
-    } for constructor in interface.custom_constructors]
-
-    # [EventConstructor]
-    has_event_constructor = 'EventConstructor' in extended_attributes
-    any_type_attributes = [attribute for attribute in interface.attributes
-                           if attribute.idl_type.name == 'Any']
-    if has_event_constructor:
-        includes.add('bindings/core/v8/Dictionary.h')
-        if any_type_attributes:
-            includes.add('bindings/core/v8/SerializedScriptValue.h')
-
-    # [NamedConstructor]
-    named_constructor = named_constructor_context(interface)
-
-    if (constructors or custom_constructors or has_event_constructor or
-        named_constructor):
-        includes.add('bindings/core/v8/V8ObjectConstructor.h')
-        includes.add('core/frame/LocalDOMWindow.h')
-
-    context.update({
-        'any_type_attributes': any_type_attributes,
-        'constructors': constructors,
-        'has_custom_constructor': bool(custom_constructors),
-        'has_event_constructor': has_event_constructor,
-        'interface_length':
-            interface_length(interface, constructors + custom_constructors),
-        'is_constructor_raises_exception': extended_attributes.get('RaisesException') == 'Constructor',  # [RaisesException=Constructor]
-        'named_constructor': named_constructor,
-    })
-
-    constants = [constant_context(constant) for constant in interface.constants]
-
-    # Constants
-    context.update({
-        'constants': constants,
-        'do_not_check_constants': 'DoNotCheckConstants' in extended_attributes,
-        'has_constant_configuration': any(
-            not constant['runtime_enabled_function']
-            for constant in constants),
-    })
-
-    # Attributes
-    attributes = [v8_attributes.attribute_context(interface, attribute)
-                  for attribute in interface.attributes]
-    context.update({
-        'attributes': attributes,
-        'has_accessors': any(attribute['is_expose_js_accessors'] and attribute['should_be_exposed_to_script'] for attribute in attributes),
-        'has_attribute_configuration': any(
-             not (attribute['is_expose_js_accessors'] or
-                  attribute['is_static'] or
-                  attribute['runtime_enabled_function'])
-             and attribute['should_be_exposed_to_script']
-             for attribute in attributes),
-        'has_conditional_attributes': any(attribute['exposed_test'] for attribute in attributes),
-        'has_constructor_attributes': any(attribute['constructor_type'] for attribute in attributes),
-        'has_replaceable_attributes': any(attribute['is_replaceable'] for attribute in attributes),
-    })
-
-    # Methods
-    methods = [v8_methods.method_context(interface, method)
-               for method in interface.operations
-               if method.name]  # Skip anonymous special operations (methods)
-    compute_method_overloads_context(methods)
-
-    # Stringifier
-    if interface.stringifier:
-        stringifier = interface.stringifier
-        method = IdlOperation(interface.idl_name)
-        method.name = 'toString'
-        method.idl_type = IdlType('DOMString')
-        method.extended_attributes.update(stringifier.extended_attributes)
-        if stringifier.attribute:
-            method.extended_attributes['ImplementedAs'] = stringifier.attribute.name
-        elif stringifier.operation:
-            method.extended_attributes['ImplementedAs'] = stringifier.operation.name
-        methods.append(v8_methods.method_context(interface, method))
-
-    conditionally_enabled_methods = []
-    custom_registration_methods = []
-    method_configuration_methods = []
-
-    for method in methods:
-        # Skip all but one method in each set of overloaded methods.
-        if 'overload_index' in method and 'overloads' not in method:
-            continue
-
-        if 'overloads' in method:
-            overloads = method['overloads']
-            conditionally_exposed_function = overloads['exposed_test_all']
-            runtime_enabled_function = overloads['runtime_enabled_function_all']
-            has_custom_registration = overloads['has_custom_registration_all']
-        else:
-            conditionally_exposed_function = method['exposed_test']
-            runtime_enabled_function = method['runtime_enabled_function']
-            has_custom_registration = method['has_custom_registration']
-
-        if conditionally_exposed_function:
-            conditionally_enabled_methods.append(method)
-            continue
-        if runtime_enabled_function or has_custom_registration:
-            custom_registration_methods.append(method)
-            continue
-        if method['should_be_exposed_to_script']:
-            method_configuration_methods.append(method)
-
-    for method in methods:
-        # The value of the Function object’s “length” property is a Number
-        # determined as follows:
-        # 1. Let S be the effective overload set for regular operations (if the
-        # operation is a regular operation) or for static operations (if the
-        # operation is a static operation) with identifier id on interface I and
-        # with argument count 0.
-        # 2. Return the length of the shortest argument list of the entries in S.
-        # FIXME: This calculation doesn't take into account whether runtime
-        # enabled overloads are actually enabled, so length may be incorrect.
-        # E.g., [RuntimeEnabled=Foo] void f(); void f(long x);
-        # should have length 1 if Foo is not enabled, but length 0 if it is.
-        method['length'] = (method['overloads']['minarg'] if 'overloads' in method else
-                            method['number_of_required_arguments'])
-
-    context.update({
-        'conditionally_enabled_methods': conditionally_enabled_methods,
-        'custom_registration_methods': custom_registration_methods,
-        'has_origin_safe_method_setter': any(
-            method['is_check_security_for_frame'] and not method['is_read_only']
-            for method in methods),
-        'has_private_script': any(attribute['is_implemented_in_private_script'] for attribute in attributes) or
-            any(method['is_implemented_in_private_script'] for method in methods),
-        'method_configuration_methods': method_configuration_methods,
-        'methods': methods,
-    })
-
-    context.update({
-        'indexed_property_getter': indexed_property_getter(interface),
-        'indexed_property_setter': indexed_property_setter(interface),
-        'indexed_property_deleter': indexed_property_deleter(interface),
-        'is_override_builtins': 'OverrideBuiltins' in extended_attributes,
-        'named_property_getter': named_property_getter(interface),
-        'named_property_setter': named_property_setter(interface),
-        'named_property_deleter': named_property_deleter(interface),
-    })
-
-    return context
-
-
-# [DeprecateAs], [Reflect], [RuntimeEnabled]
-def constant_context(constant):
-    # (Blink-only) string literals are unquoted in tokenizer, must be re-quoted
-    # in C++.
-    if constant.idl_type.name == 'String':
-        value = '"%s"' % constant.value
-    else:
-        value = constant.value
-
-    extended_attributes = constant.extended_attributes
-    return {
-        'cpp_class': extended_attributes.get('PartialInterfaceImplementedAs'),
-        'idl_type': constant.idl_type.name,
-        'name': constant.name,
-        # FIXME: use 'reflected_name' as correct 'name'
-        'reflected_name': extended_attributes.get('Reflect', constant.name),
-        'runtime_enabled_function': runtime_enabled_function_name(constant),
-        'value': value,
-    }
-
-
-################################################################################
-# Overloads
-################################################################################
-
-def compute_method_overloads_context(methods):
-    # Regular methods
-    compute_method_overloads_context_by_type([method for method in methods
-                                              if not method['is_static']])
-    # Static methods
-    compute_method_overloads_context_by_type([method for method in methods
-                                              if method['is_static']])
-
-
-def compute_method_overloads_context_by_type(methods):
-    """Computes |method.overload*| template values.
-
-    Called separately for static and non-static (regular) methods,
-    as these are overloaded separately.
-    Modifies |method| in place for |method| in |methods|.
-    Doesn't change the |methods| list itself (only the values, i.e. individual
-    methods), so ok to treat these separately.
-    """
-    # Add overload information only to overloaded methods, so template code can
-    # easily verify if a function is overloaded
-    for name, overloads in method_overloads_by_name(methods):
-        # Resolution function is generated after last overloaded function;
-        # package necessary information into |method.overloads| for that method.
-        overloads[-1]['overloads'] = overloads_context(overloads)
-        overloads[-1]['overloads']['name'] = name
-
-
-def method_overloads_by_name(methods):
-    """Returns generator of overloaded methods by name: [name, [method]]"""
-    # Filter to only methods that are actually overloaded
-    method_counts = Counter(method['name'] for method in methods)
-    overloaded_method_names = set(name
-                                  for name, count in method_counts.iteritems()
-                                  if count > 1)
-    overloaded_methods = [method for method in methods
-                          if method['name'] in overloaded_method_names]
-
-    # Group by name (generally will be defined together, but not necessarily)
-    return sort_and_groupby(overloaded_methods, itemgetter('name'))
-
-
-def overloads_context(overloads):
-    """Returns |overloads| template values for a single name.
-
-    Sets |method.overload_index| in place for |method| in |overloads|
-    and returns dict of overall overload template values.
-    """
-    assert len(overloads) > 1  # only apply to overloaded names
-    for index, method in enumerate(overloads, 1):
-        method['overload_index'] = index
-
-    effective_overloads_by_length = effective_overload_set_by_length(overloads)
-    lengths = [length for length, _ in effective_overloads_by_length]
-    name = overloads[0].get('name', '<constructor>')
-
-    # Check and fail if all overloads with the shortest acceptable arguments
-    # list are runtime enabled, since we would otherwise set 'length' on the
-    # function object to an incorrect value when none of those overloads were
-    # actually enabled at runtime. The exception is if all overloads are
-    # controlled by the same runtime enabled feature, in which case there would
-    # be no function object at all if it is not enabled.
-    shortest_overloads = effective_overloads_by_length[0][1]
-    if (all(method.get('runtime_enabled_function')
-            for method, _, _ in shortest_overloads) and
-        not common_value(overloads, 'runtime_enabled_function')):
-        raise ValueError('Function.length of %s depends on runtime enabled features' % name)
-
-    # Check and fail if overloads disagree on any of the extended attributes
-    # that affect how the method should be registered.
-    # Skip the check for overloaded constructors, since they don't support any
-    # of the extended attributes in question.
-    if not overloads[0].get('is_constructor'):
-        overload_extended_attributes = [
-            method['custom_registration_extended_attributes']
-            for method in overloads]
-        for extended_attribute in v8_methods.CUSTOM_REGISTRATION_EXTENDED_ATTRIBUTES:
-            if common_key(overload_extended_attributes, extended_attribute) is None:
-                raise ValueError('Overloads of %s have conflicting extended attribute %s'
-                                 % (name, extended_attribute))
-
-    # Check and fail if overloads disagree about whether the return type
-    # is a Promise or not.
-    promise_overload_count = sum(1 for method in overloads if method.get('idl_type') == 'Promise')
-    if promise_overload_count not in (0, len(overloads)):
-        raise ValueError('Overloads of %s have conflicting Promise/non-Promise types'
-                         % (name))
-
-    return {
-        'deprecate_all_as': common_value(overloads, 'deprecate_as'),  # [DeprecateAs]
-        'exposed_test_all': common_value(overloads, 'exposed_test'),  # [Exposed]
-        'has_custom_registration_all': common_value(overloads, 'has_custom_registration'),
-        'length_tests_methods': length_tests_methods(effective_overloads_by_length),
-        # 1. Let maxarg be the length of the longest type list of the
-        # entries in S.
-        'maxarg': lengths[-1],
-        'measure_all_as': common_value(overloads, 'measure_as'),  # [MeasureAs]
-        'minarg': lengths[0],
-        'runtime_enabled_function_all': common_value(overloads, 'runtime_enabled_function'),  # [RuntimeEnabled]
-        'valid_arities': lengths
-            # Only need to report valid arities if there is a gap in the
-            # sequence of possible lengths, otherwise invalid length means
-            # "not enough arguments".
-            if lengths[-1] - lengths[0] != len(lengths) - 1 else None,
-    }
-
-
-def effective_overload_set(F):
-    """Returns the effective overload set of an overloaded function.
-
-    An effective overload set is the set of overloaded functions + signatures
-    (type list of arguments, with optional and variadic arguments included or
-    not), and is used in the overload resolution algorithm.
-
-    For example, given input [f1(optional long x), f2(DOMString s)], the output
-    is informally [f1(), f1(long), f2(DOMString)], and formally
-    [(f1, [], []), (f1, [long], [optional]), (f2, [DOMString], [required])].
-
-    Currently the optionality list is a list of |is_optional| booleans (True
-    means optional, False means required); to support variadics this needs to
-    be tri-valued as required, optional, or variadic.
-
-    Formally:
-    An effective overload set represents the allowable invocations for a
-    particular operation, constructor (specified with [Constructor] or
-    [NamedConstructor]), legacy caller or callback function.
-
-    An additional argument N (argument count) is needed when overloading
-    variadics, but we don't use that currently.
-
-    Spec: http://heycam.github.io/webidl/#dfn-effective-overload-set
-
-    Formally the input and output lists are sets, but methods are stored
-    internally as dicts, which can't be stored in a set because they are not
-    hashable, so we use lists instead.
-
-    Arguments:
-        F: list of overloads for a given callable name.
-
-    Returns:
-        S: list of tuples of the form (callable, type list, optionality list).
-    """
-    # Code closely follows the algorithm in the spec, for clarity and
-    # correctness, and hence is not very Pythonic.
-
-    # 1. Initialize S to ∅.
-    # (We use a list because we can't use a set, as noted above.)
-    S = []
-
-    # 2. Let F be a set with elements as follows, according to the kind of
-    # effective overload set:
-    # (Passed as argument, nothing to do.)
-
-    # 3. & 4. (maxarg, m) are only needed for variadics, not used.
-
-    # 5. For each operation, extended attribute or callback function X in F:
-    for X in F:  # X is the "callable", F is the overloads.
-        arguments = X['arguments']
-        # 1. Let n be the number of arguments X is declared to take.
-        n = len(arguments)
-        # 2. Let t0..n−1 be a list of types, where ti is the type of X’s
-        # argument at index i.
-        # (“type list”)
-        t = tuple(argument['idl_type_object'] for argument in arguments)
-        # 3. Let o0..n−1 be a list of optionality values, where oi is “variadic”
-        # if X’s argument at index i is a final, variadic argument, “optional”
-        # if the argument is optional, and “required” otherwise.
-        # (“optionality list”)
-        # (We’re just using a boolean for optional vs. required.)
-        o = tuple(argument['is_optional'] for argument in arguments)
-        # 4. Add to S the tuple <X, t0..n−1, o0..n−1>.
-        S.append((X, t, o))
-        # 5. If X is declared to be variadic, then:
-        # (Not used, so not implemented.)
-        # 6. Initialize i to n−1.
-        i = n - 1
-        # 7. While i ≥ 0:
-        # Spec bug (fencepost error); should be “While i > 0:”
-        # https://www.w3.org/Bugs/Public/show_bug.cgi?id=25590
-        while i > 0:
-            # 1. If argument i of X is not optional, then break this loop.
-            if not o[i]:
-                break
-            # 2. Otherwise, add to S the tuple <X, t0..i−1, o0..i−1>.
-            S.append((X, t[:i], o[:i]))
-            # 3. Set i to i−1.
-            i = i - 1
-        # 8. If n > 0 and all arguments of X are optional, then add to S the
-        # tuple <X, (), ()> (where “()” represents the empty list).
-        if n > 0 and all(oi for oi in o):
-            S.append((X, [], []))
-    # 6. The effective overload set is S.
-    return S
-
-
-def effective_overload_set_by_length(overloads):
-    def type_list_length(entry):
-        # Entries in the effective overload set are 3-tuples:
-        # (callable, type list, optionality list)
-        return len(entry[1])
-
-    effective_overloads = effective_overload_set(overloads)
-    return list(sort_and_groupby(effective_overloads, type_list_length))
-
-
-def distinguishing_argument_index(entries):
-    """Returns the distinguishing argument index for a sequence of entries.
-
-    Entries are elements of the effective overload set with the same number
-    of arguments (formally, same type list length), each a 3-tuple of the form
-    (callable, type list, optionality list).
-
-    Spec: http://heycam.github.io/webidl/#dfn-distinguishing-argument-index
-
-    If there is more than one entry in an effective overload set that has a
-    given type list length, then for those entries there must be an index i
-    such that for each pair of entries the types at index i are
-    distinguishable.
-    The lowest such index is termed the distinguishing argument index for the
-    entries of the effective overload set with the given type list length.
-    """
-    # Only applicable “If there is more than one entry”
-    assert len(entries) > 1
-    type_lists = [tuple(idl_type.name for idl_type in entry[1])
-                  for entry in entries]
-    type_list_length = len(type_lists[0])
-    # Only applicable for entries that “[have] a given type list length”
-    assert all(len(type_list) == type_list_length for type_list in type_lists)
-    name = entries[0][0].get('name', 'Constructor')  # for error reporting
-
-    # The spec defines the distinguishing argument index by conditions it must
-    # satisfy, but does not give an algorithm.
-    #
-    # We compute the distinguishing argument index by first computing the
-    # minimum index where not all types are the same, and then checking that
-    # all types in this position are distinguishable (and the optionality lists
-    # up to this point are identical), since "minimum index where not all types
-    # are the same" is a *necessary* condition, and more direct to check than
-    # distinguishability.
-    types_by_index = (set(types) for types in zip(*type_lists))
-    try:
-        # “In addition, for each index j, where j is less than the
-        #  distinguishing argument index for a given type list length, the types
-        #  at index j in all of the entries’ type lists must be the same”
-        index = next(i for i, types in enumerate(types_by_index)
-                     if len(types) > 1)
-    except StopIteration:
-        raise ValueError('No distinguishing index found for %s, length %s:\n'
-                         'All entries have the same type list:\n'
-                         '%s' % (name, type_list_length, type_lists[0]))
-    # Check optionality
-    # “and the booleans in the corresponding list indicating argument
-    #  optionality must be the same.”
-    # FIXME: spec typo: optionality value is no longer a boolean
-    # https://www.w3.org/Bugs/Public/show_bug.cgi?id=25628
-    initial_optionality_lists = set(entry[2][:index] for entry in entries)
-    if len(initial_optionality_lists) > 1:
-        raise ValueError(
-            'Invalid optionality lists for %s, length %s:\n'
-            'Optionality lists differ below distinguishing argument index %s:\n'
-            '%s'
-            % (name, type_list_length, index, set(initial_optionality_lists)))
-
-    # Check distinguishability
-    # http://heycam.github.io/webidl/#dfn-distinguishable
-    # Use names to check for distinct types, since objects are distinct
-    # FIXME: check distinguishability more precisely, for validation
-    distinguishing_argument_type_names = [type_list[index]
-                                          for type_list in type_lists]
-    if (len(set(distinguishing_argument_type_names)) !=
-        len(distinguishing_argument_type_names)):
-        raise ValueError('Types in distinguishing argument are not distinct:\n'
-                         '%s' % distinguishing_argument_type_names)
-
-    return index
-
-
-def length_tests_methods(effective_overloads_by_length):
-    """Returns sorted list of resolution tests and associated methods, by length.
-
-    This builds the main data structure for the overload resolution loop.
-    For a given argument length, bindings test argument at distinguishing
-    argument index, in order given by spec: if it is compatible with
-    (optionality or) type required by an overloaded method, resolve to that
-    method.
-
-    Returns:
-        [(length, [(test, method)])]
-    """
-    return [(length, list(resolution_tests_methods(effective_overloads)))
-            for length, effective_overloads in effective_overloads_by_length]
-
-
-def resolution_tests_methods(effective_overloads):
-    """Yields resolution test and associated method, in resolution order, for effective overloads of a given length.
-
-    This is the heart of the resolution algorithm.
-    http://heycam.github.io/webidl/#dfn-overload-resolution-algorithm
-
-    Note that a given method can be listed multiple times, with different tests!
-    This is to handle implicit type conversion.
-
-    Returns:
-        [(test, method)]
-    """
-    methods = [effective_overload[0]
-               for effective_overload in effective_overloads]
-    if len(methods) == 1:
-        # If only one method with a given length, no test needed
-        yield 'true', methods[0]
-        return
-
-    # 6. If there is more than one entry in S, then set d to be the
-    # distinguishing argument index for the entries of S.
-    index = distinguishing_argument_index(effective_overloads)
-    # (7-9 are for handling |undefined| values for optional arguments before
-    # the distinguishing argument (as “missing”), so you can specify only some
-    # optional arguments. We don’t support this, so we skip these steps.)
-    # 10. If i = d, then:
-    # (d is the distinguishing argument index)
-    # 1. Let V be argi.
-    #     Note: This is the argument that will be used to resolve which
-    #           overload is selected.
-    cpp_value = 'info[%s]' % index
-
-    # Extract argument and IDL type to simplify accessing these in each loop.
-    arguments = [method['arguments'][index] for method in methods]
-    arguments_methods = zip(arguments, methods)
-    idl_types = [argument['idl_type_object'] for argument in arguments]
-    idl_types_methods = zip(idl_types, methods)
-
-    # We can’t do a single loop through all methods or simply sort them, because
-    # a method may be listed in multiple steps of the resolution algorithm, and
-    # which test to apply differs depending on the step.
-    #
-    # Instead, we need to go through all methods at each step, either finding
-    # first match (if only one test is allowed) or filtering to matches (if
-    # multiple tests are allowed), and generating an appropriate tests.
-
-    # 2. If V is undefined, and there is an entry in S whose list of
-    # optionality values has “optional” at index i, then remove from S all
-    # other entries.
-    try:
-        method = next(method for argument, method in arguments_methods
-                      if argument['is_optional'])
-        test = '%s->IsUndefined()' % cpp_value
-        yield test, method
-    except StopIteration:
-        pass
-
-    # 3. Otherwise: if V is null or undefined, and there is an entry in S that
-    # has one of the following types at position i of its type list,
-    # • a nullable type
-    try:
-        method = next(method for idl_type, method in idl_types_methods
-                      if idl_type.is_nullable)
-        test = 'isUndefinedOrNull(%s)' % cpp_value
-        yield test, method
-    except StopIteration:
-        pass
-
-    # 4. Otherwise: if V is a platform object – but not a platform array
-    # object – and there is an entry in S that has one of the following
-    # types at position i of its type list,
-    # • an interface type that V implements
-    # (Unlike most of these tests, this can return multiple methods, since we
-    #  test if it implements an interface. Thus we need a for loop, not a next.)
-    # (We distinguish wrapper types from built-in interface types.)
-    for idl_type, method in ((idl_type, method)
-                             for idl_type, method in idl_types_methods
-                             if idl_type.is_wrapper_type):
-        test = 'V8{idl_type}::hasInstance({cpp_value}, info.GetIsolate())'.format(idl_type=idl_type.base_type, cpp_value=cpp_value)
-        yield test, method
-
-    # 8. Otherwise: if V is any kind of object except for a native Date object,
-    # a native RegExp object, and there is an entry in S that has one of the
-    # following types at position i of its type list,
-    # • an array type
-    # • a sequence type
-    # ...
-    # • a dictionary
-    try:
-        idl_type, method = next((idl_type, method)
-                                for idl_type, method in idl_types_methods
-                                if (idl_type.native_array_element_type or
-                                    idl_type.is_dictionary or
-                                    idl_type.name == 'Dictionary'))
-        if idl_type.native_array_element_type:
-            # (We test for Array instead of generic Object to type-check.)
-            # FIXME: test for Object during resolution, then have type check for
-            # Array in overloaded method: http://crbug.com/262383
-            test = '%s->IsArray()' % cpp_value
-        else:
-            # FIXME: should be '{1}->IsObject() && !{1}->IsDate() && !{1}->IsRegExp()'.format(cpp_value)
-            # FIXME: the IsDate and IsRegExp checks can be skipped if we've
-            # already generated tests for them.
-            test = '%s->IsObject()' % cpp_value
-        yield test, method
-    except StopIteration:
-        pass
-
-    # (Check for exact type matches before performing automatic type conversion;
-    # only needed if distinguishing between primitive types.)
-    if len([idl_type.is_primitive_type for idl_type in idl_types]) > 1:
-        # (Only needed if match in step 11, otherwise redundant.)
-        if any(idl_type.is_string_type or idl_type.is_enum
-               for idl_type in idl_types):
-            # 10. Otherwise: if V is a Number value, and there is an entry in S
-            # that has one of the following types at position i of its type
-            # list,
-            # • a numeric type
-            try:
-                method = next(method for idl_type, method in idl_types_methods
-                              if idl_type.is_numeric_type)
-                test = '%s->IsNumber()' % cpp_value
-                yield test, method
-            except StopIteration:
-                pass
-
-    # (Perform automatic type conversion, in order. If any of these match,
-    # that’s the end, and no other tests are needed.) To keep this code simple,
-    # we rely on the C++ compiler's dead code elimination to deal with the
-    # redundancy if both cases below trigger.
-
-    # 11. Otherwise: if there is an entry in S that has one of the following
-    # types at position i of its type list,
-    # • DOMString
-    # • ByteString
-    # • ScalarValueString [a DOMString typedef, per definition.]
-    # • an enumeration type
-    try:
-        method = next(method for idl_type, method in idl_types_methods
-                      if idl_type.is_string_type or idl_type.is_enum)
-        yield 'true', method
-    except StopIteration:
-        pass
-
-    # 12. Otherwise: if there is an entry in S that has one of the following
-    # types at position i of its type list,
-    # • a numeric type
-    try:
-        method = next(method for idl_type, method in idl_types_methods
-                      if idl_type.is_numeric_type)
-        yield 'true', method
-    except StopIteration:
-        pass
-
-
-################################################################################
-# Utility functions
-################################################################################
-
-def Counter(iterable):
-    # Once using Python 2.7, using collections.Counter
-    counter = defaultdict(lambda: 0)
-    for item in iterable:
-        counter[item] += 1
-    return counter
-
-
-def common(dicts, f):
-    """Returns common result of f across an iterable of dicts, or None.
-
-    Call f for each dict and return its result if the same across all dicts.
-    """
-    values = (f(d) for d in dicts)
-    first_value = next(values)
-    if all(value == first_value for value in values):
-        return first_value
-    return None
-
-
-def common_key(dicts, key):
-    """Returns common presence of a key across an iterable of dicts, or None.
-
-    True if all dicts have the key, False if none of the dicts have the key,
-    and None if some but not all dicts have the key.
-    """
-    return common(dicts, lambda d: key in d)
-
-
-def common_value(dicts, key):
-    """Returns common value of a key across an iterable of dicts, or None.
-
-    Auxiliary function for overloads, so can consolidate an extended attribute
-    that appears with the same value on all items in an overload set.
-    """
-    return common(dicts, lambda d: d.get(key))
-
-
-def sort_and_groupby(l, key=None):
-    """Returns a generator of (key, list), sorting and grouping list by key."""
-    l.sort(key=key)
-    return ((k, list(g)) for k, g in itertools.groupby(l, key))
-
-
-################################################################################
-# Constructors
-################################################################################
-
-# [Constructor]
-def constructor_context(interface, constructor):
-    arguments_need_try_catch = any(v8_methods.argument_needs_try_catch(constructor, argument)
-                                   for argument in constructor.arguments)
-
-    # [RaisesException=Constructor]
-    is_constructor_raises_exception = \
-        interface.extended_attributes.get('RaisesException') == 'Constructor'
-
-    return {
-        'arguments': [v8_methods.argument_context(interface, constructor, argument, index)
-                      for index, argument in enumerate(constructor.arguments)],
-        'arguments_need_try_catch': arguments_need_try_catch,
-        'cpp_type': cpp_template_type(
-            'RefPtr',
-            cpp_name(interface)),
-        'cpp_value': v8_methods.cpp_value(
-            interface, constructor, len(constructor.arguments)),
-        'has_exception_state':
-            is_constructor_raises_exception or
-            any(argument for argument in constructor.arguments
-                if argument.idl_type.name == 'SerializedScriptValue' or
-                   argument.idl_type.may_raise_exception_on_conversion),
-        'is_call_with_document':
-            # [ConstructorCallWith=Document]
-            has_extended_attribute_value(interface,
-                'ConstructorCallWith', 'Document'),
-        'is_call_with_execution_context':
-            # [ConstructorCallWith=ExecutionContext]
-            has_extended_attribute_value(interface,
-                'ConstructorCallWith', 'ExecutionContext'),
-        'is_constructor': True,
-        'is_named_constructor': False,
-        'is_raises_exception': is_constructor_raises_exception,
-        'number_of_required_arguments':
-            number_of_required_arguments(constructor),
-    }
-
-
-# [NamedConstructor]
-def named_constructor_context(interface):
-    extended_attributes = interface.extended_attributes
-    if 'NamedConstructor' not in extended_attributes:
-        return None
-    # FIXME: parser should return named constructor separately;
-    # included in constructors (and only name stored in extended attribute)
-    # for Perl compatibility
-    idl_constructor = interface.constructors[-1]
-    assert idl_constructor.name == 'NamedConstructor'
-    context = constructor_context(interface, idl_constructor)
-    context.update({
-        'name': extended_attributes['NamedConstructor'],
-        'is_named_constructor': True,
-    })
-    return context
-
-
-def number_of_required_arguments(constructor):
-    return len([argument for argument in constructor.arguments
-                if not argument.is_optional])
-
-
-def interface_length(interface, constructors):
-    # Docs: http://heycam.github.io/webidl/#es-interface-call
-    if 'EventConstructor' in interface.extended_attributes:
-        return 1
-    if not constructors:
-        return 0
-    return min(constructor['number_of_required_arguments']
-               for constructor in constructors)
-
-
-################################################################################
-# Special operations (methods)
-# http://heycam.github.io/webidl/#idl-special-operations
-################################################################################
-
-def property_getter(getter, cpp_arguments):
-    def is_null_expression(idl_type):
-        if idl_type.is_union_type:
-            notnull = ' || '.join([
-                    member_argument['null_check_value']
-                    for member_argument in idl_type.union_arguments])
-            return '!(%s)' % notnull
-        if idl_type.name == 'String':
-            return 'result.isNull()'
-        if idl_type.is_interface_type:
-            return '!result'
-        return ''
-
-    idl_type = getter.idl_type
-    extended_attributes = getter.extended_attributes
-    is_raises_exception = 'RaisesException' in extended_attributes
-
-    # FIXME: make more generic, so can use v8_methods.cpp_value
-    cpp_method_name = 'impl->%s' % cpp_name(getter)
-
-    if is_raises_exception:
-        cpp_arguments.append('exceptionState')
-    union_arguments = idl_type.union_arguments
-    if union_arguments:
-        cpp_arguments.extend([member_argument['cpp_value']
-                              for member_argument in union_arguments])
-
-    cpp_value = '%s(%s)' % (cpp_method_name, ', '.join(cpp_arguments))
-
-    return {
-        'cpp_type': idl_type.cpp_type,
-        'cpp_value': cpp_value,
-        'is_custom':
-            'Custom' in extended_attributes and
-            (not extended_attributes['Custom'] or
-             has_extended_attribute_value(getter, 'Custom', 'PropertyGetter')),
-        'is_custom_property_enumerator': has_extended_attribute_value(
-            getter, 'Custom', 'PropertyEnumerator'),
-        'is_custom_property_query': has_extended_attribute_value(
-            getter, 'Custom', 'PropertyQuery'),
-        'is_enumerable': 'NotEnumerable' not in extended_attributes,
-        'is_null_expression': is_null_expression(idl_type),
-        'is_raises_exception': is_raises_exception,
-        'name': cpp_name(getter),
-        'union_arguments': union_arguments,
-        'v8_set_return_value': idl_type.v8_set_return_value('result', extended_attributes=extended_attributes, script_wrappable='impl', release=idl_type.release),
-    }
-
-
-def property_setter(setter):
-    idl_type = setter.arguments[1].idl_type
-    extended_attributes = setter.extended_attributes
-    is_raises_exception = 'RaisesException' in extended_attributes
-    return {
-        'has_type_checking_interface':
-            has_extended_attribute_value(setter, 'TypeChecking', 'Interface') and
-            idl_type.is_wrapper_type,
-        'idl_type': idl_type.base_type,
-        'is_custom': 'Custom' in extended_attributes,
-        'has_exception_state': is_raises_exception or
-                               idl_type.is_integer_type,
-        'is_raises_exception': is_raises_exception,
-        'name': cpp_name(setter),
-        'v8_value_to_local_cpp_value': idl_type.v8_value_to_local_cpp_value(
-            extended_attributes, 'v8Value', 'propertyValue'),
-    }
-
-
-def property_deleter(deleter):
-    idl_type = deleter.idl_type
-    if str(idl_type) != 'boolean':
-        raise Exception(
-            'Only deleters with boolean type are allowed, but type is "%s"' %
-            idl_type)
-    extended_attributes = deleter.extended_attributes
-    return {
-        'is_custom': 'Custom' in extended_attributes,
-        'is_raises_exception': 'RaisesException' in extended_attributes,
-        'name': cpp_name(deleter),
-    }
-
-
-################################################################################
-# Indexed properties
-# http://heycam.github.io/webidl/#idl-indexed-properties
-################################################################################
-
-def indexed_property_getter(interface):
-    try:
-        # Find indexed property getter, if present; has form:
-        # getter TYPE [OPTIONAL_IDENTIFIER](unsigned long ARG1)
-        getter = next(
-            method
-            for method in interface.operations
-            if ('getter' in method.specials and
-                len(method.arguments) == 1 and
-                str(method.arguments[0].idl_type) == 'unsigned long'))
-    except StopIteration:
-        return None
-
-    return property_getter(getter, ['index'])
-
-
-def indexed_property_setter(interface):
-    try:
-        # Find indexed property setter, if present; has form:
-        # setter RETURN_TYPE [OPTIONAL_IDENTIFIER](unsigned long ARG1, ARG_TYPE ARG2)
-        setter = next(
-            method
-            for method in interface.operations
-            if ('setter' in method.specials and
-                len(method.arguments) == 2 and
-                str(method.arguments[0].idl_type) == 'unsigned long'))
-    except StopIteration:
-        return None
-
-    return property_setter(setter)
-
-
-def indexed_property_deleter(interface):
-    try:
-        # Find indexed property deleter, if present; has form:
-        # deleter TYPE [OPTIONAL_IDENTIFIER](unsigned long ARG)
-        deleter = next(
-            method
-            for method in interface.operations
-            if ('deleter' in method.specials and
-                len(method.arguments) == 1 and
-                str(method.arguments[0].idl_type) == 'unsigned long'))
-    except StopIteration:
-        return None
-
-    return property_deleter(deleter)
-
-
-################################################################################
-# Named properties
-# http://heycam.github.io/webidl/#idl-named-properties
-################################################################################
-
-def named_property_getter(interface):
-    try:
-        # Find named property getter, if present; has form:
-        # getter TYPE [OPTIONAL_IDENTIFIER](DOMString ARG1)
-        getter = next(
-            method
-            for method in interface.operations
-            if ('getter' in method.specials and
-                len(method.arguments) == 1 and
-                str(method.arguments[0].idl_type) == 'DOMString'))
-    except StopIteration:
-        return None
-
-    getter.name = getter.name or 'anonymousNamedGetter'
-    return property_getter(getter, ['propertyName'])
-
-
-def named_property_setter(interface):
-    try:
-        # Find named property setter, if present; has form:
-        # setter RETURN_TYPE [OPTIONAL_IDENTIFIER](DOMString ARG1, ARG_TYPE ARG2)
-        setter = next(
-            method
-            for method in interface.operations
-            if ('setter' in method.specials and
-                len(method.arguments) == 2 and
-                str(method.arguments[0].idl_type) == 'DOMString'))
-    except StopIteration:
-        return None
-
-    return property_setter(setter)
-
-
-def named_property_deleter(interface):
-    try:
-        # Find named property deleter, if present; has form:
-        # deleter TYPE [OPTIONAL_IDENTIFIER](DOMString ARG)
-        deleter = next(
-            method
-            for method in interface.operations
-            if ('deleter' in method.specials and
-                len(method.arguments) == 1 and
-                str(method.arguments[0].idl_type) == 'DOMString'))
-    except StopIteration:
-        return None
-
-    return property_deleter(deleter)