[Cython] Cannot coerce list to type 'list'

[Muhammad Alkarouri]

2008/12/18 Robert Bradshaw <robertwb at math.washington.edu>:
> On Dec 17, 2008, at 4:25 PM, Muhammad Alkarouri wrote:
>
>> On Dec 17, 2008, Robert Bradshaw wrote:
>>
>>> What is the definition of list in c_python? If it's a cdef extern
>>> class of the actual python list, then this is a bug and should work.
>>> Also, you might not need c_python anymore.
>>
>> Thanks, that does the trick.
>> The __builtin__.list was cdef extern in the c_python.pxd (shown
>> below), I simply commented it and the code worked fine.
>> Is there a fault with how I have it written, or should I report it
>> as a bug now?
>
> I'm not sure what the best thing to do here is (certainly it could be
> fixed to ignore these extern types that match), but there's no
> advantage to declaring the empty dict and list types as Cython
> understands those types natively now.
>

I suggested to report it according to your earlier suggestion, but I
would say the best way forward for Cython is to explicitly deprecate
the practice of declaring types that are defined by Cython. Say,
cython should fail with a kind of duplicate error or 'new definition
overrides cython built in' kind of message. The idea is that:

1. The will be less hairy code and more maintainable for cython developers.
2. For a cython user like me, such a failure would be clear enough to
modify the source in accordance.
3. Cython will probably grow more capabilities in types and other
optimizations in the future. These may replace user defined ones. If
users are used to this kind of change this will give Cython developers
more leeway in doing improvements in types and functions.

In short, I would fix that by giving a clearer error and also clearly
noting that in the documentation. The user should expect to have to
delete the offending duplicate type or function. Does that make sense?


Cheers,

Muhammad