Mojo: bindings generator: Add an AST type for parameter lists.

mojo/public/tools/bindings/pylib/mojom/parse/translate.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Translates parse tree to Mojom IR."""
 
 
 import ast
 import re
 
@@ skipping 55 matching lines @@
   return out
 
 def _MapField(tree):
   assert isinstance(tree[3], ast.Ordinal)
   return {'name': tree[2],
           'kind': _MapKind(tree[1]),
           'ordinal': tree[3].value,
           'default': tree[4]}
 
 def _MapMethod(tree):
+  assert isinstance(tree[2], ast.ParameterList)
+  assert isinstance(tree[3], ast.Ordinal)
+  assert tree[4] is None or isinstance(tree[2], ast.ParameterList)
+
   def ParameterToDict(param):
     assert isinstance(param, ast.Parameter)
     return {'name': param.name,
             'kind': _MapKind(param.typename),
             'ordinal': param.ordinal.value}
 
-  assert isinstance(tree[2], list)
-  assert isinstance(tree[3], ast.Ordinal)
   method = {'name': tree[1],
             'parameters': map(ParameterToDict, tree[2]),
             'ordinal': tree[3].value}
-  # Note: |tree[4]| may be an empty list, indicating a parameter-less response.
-  if tree[4] is not None:
+  if tree[4]:
     method['response_parameters'] = map(ParameterToDict, tree[4])
   return method
 
 def _MapEnumField(tree):
   return {'name': tree[1],
           'value': tree[2]}
 
 def _MapStruct(tree):
   struct = {}
   struct['name'] = tree[1]
@@ skipping 50 matching lines @@
     modules = [_MapModule(item, name) for item in tree if item[0] == 'MODULE']
     if len(modules) != 1:
       raise Exception('A mojom file must contain exactly 1 module.')
     self.mojom = modules[0]
     self.mojom['imports'] = _MapTree(_MapImport, tree, 'IMPORT')
     return self.mojom
 
 
 def Translate(tree, name):
   return _MojomBuilder().Build(tree, name)