Add a missing const_cast if the parameter is const.

examples/foomodulegen.py

@@ -139,7 +139,8 @@ def my_module_gen(out_file):
 
     SomeObject.add_method(CppMethod(
             ReturnValue.new('std::string'), 'get_prefix_with_foo_ref',
-            [Parameter.new('Foo&', 'foo', is_const=True)],
+            [Parameter.new('Foo&', 'foo', is_const=True,
+                           direction=Parameter.DIRECTION_INOUT)],
             is_virtual=True, is_const=True))
 
     #SomeObject.add_method(CppMethod(

pybindgen/cppclass.py

@@ -915,8 +915,12 @@ class CppClassRefParameter(CppClassParameterBase):
             ## the ->obj pointer after the python call; this is so
             ## that the python code directly manipulates the object
             ## received as parameter, instead of a copy.
+            if self.is_const:
+                value = "const_cast<%s*>(&(%s))" % (self.cpp_class.full_name, self.value)
+            else:
+                value = "&(%s)" % self.value
             wrapper.before_call.write_code(
-                "%s->obj = &(%s);" % (self.py_name, self.value))
+                "%s->obj = %s;" % (self.py_name, value))
             wrapper.build_params.add_parameter("O", [self.py_name])
             wrapper.before_call.add_cleanup_code("Py_DECREF(%s);" % self.py_name)