[Cython] non-virtual methods

[Vitja Makarov]

2011/8/30 Robert Bradshaw <robertwb at math.washington.edu>:
> On Tue, Aug 30, 2011 at 10:19 AM, Vitja Makarov <vitja.makarov at gmail.com> wrote:
>> 2011/8/30 Stefan Behnel <stefan_ml at behnel.de>:
>>> Vitja Makarov, 30.08.2011 18:39:
>>>>
>>>> 2011/8/30 Stefan Behnel:
>>>>>
>>>>> Robert Bradshaw, 30.08.2011 18:18:
>>>>>>
>>>>>> On Tue, Aug 30, 2011 at 9:14 AM, Vitja Makarov wrote:
>>>>>>>
>>>>>>> What about final classes with cpdef methods?
>>>>>>>
>>>>>>> @cython.final
>>>>>>> class Foo:
>>>>>>>    cpdef bar(self):
>>>>>>>        pass
>>>>>>>
>>>>>>> Should that raise an error?
>>>>>>
>>>>>> That should be perfectly fine.
>>>>>
>>>>> Well, the 'final' decorator shouldn't work on normal Python classes.
>>>>>
>>>>> Regarding extension types, CPython has a way of declaring them 'final'
>>>>> with
>>>>> a type flag, which effectively prevents them from being subclassed in
>>>>> Python. So the above works as just fine for cdef classes.
>>>>>
>>>>
>>>> Ok. So final class could have cpdef methods but non-final extension
>>>> type couldn't, am I right?
>>>
>>> All extension types can have cpdef methods, be they final or not. For final
>>> classes, cpdef methods simply mean that they have a Python wrapper and will
>>> otherwise be called directly when called from Cython.
>>>
>>> Actually, for cpdef methods in final classes, we can even drop the override
>>> check in the DefNode wrapper. I don't think that currently happens.
>>>
>>
>> Currently I drop OverrideCheckNode for all final cpdef methods, see
>> https://github.com/cython/cython/pull/59/files#L2R1751
>>
>> Final classes can have cpdef method that's ok.
>> Could non-final classes have final-cpdef methods?
>
> No, as we can't prevent them from being overridden (violating the
> semantics of final). We should raise an error when trying to declare
> final cpdef methods in non-final classes.
>

Ok. I get it!


>> Currently final class means that all its c[p]def methods are final too.
>
> Good point.
>

I've updated my branch. Please review:

https://github.com/cython/cython/pull/59

I've also added PyrexType.is_final_type attribute so now it should be
used to check whether type is final or not.

-- 
vitja.