On 10 November 2017 at 18:39, Koos Zevenhoven <k7hoven@gmail.com> wrote:

On Wed, Sep 27, 2017 at 12:28 PM, Ivan Levkivskyi <levkivskyi@gmail.com> wrote:

After creating the class,
the original bases are saved in ``__orig_bases__`` (currently this is also
done by the metaclass).

Those are *still* bases, right, even if they are not in the mro? I'm not sure if this is a naming thing or something even more.

The objects that have __subclass_base__ method (proposed to rename to __mro_entry__)

are removed from __bases__ attributed of the newly created class. Otherwise they may cause a metaclass conflict.

One can however still call them syntactic (or static?) bases. For example this is how it is going to be used by typing:

from typing import List

class Tokens(List[int]):

...

assert Tokens.__bases__ == (list,)

NOTE: These two method names are reserved for exclusive use by
the ``typing`` module and the generic types machinery, and any other use is
strongly discouraged.

Given the situation, that may be a good thing. But will it really work? I think it is also strongly discouraged to invent your own dunder method names, but people still do it.

Terry had a similar comment. I will "soften" this formulation in the next revision of the PEP.

Ivan