On 10 November 2017 at 21:19, Koos Zevenhoven <k7ho...@gmail.com> wrote:
> On Fri, Nov 10, 2017 at 8:33 PM, Ivan Levkivskyi <levkivs...@gmail.com> > wrote: > >> On 10 November 2017 at 18:39, Koos Zevenhoven <k7ho...@gmail.com> wrote: >> >>> On Wed, Sep 27, 2017 at 12:28 PM, Ivan Levkivskyi <levkivs...@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,) >> > > Why is List[int] not allowed to be the base? Neither method-lookup > performance nor the metaclass conflict issue seem to depend on whether > List[int] is in __bases__. > > The situation is actually quite opposite. Interestingly, the whole discussion started from Mark Shannon pointing to these problems with List[int] at the Language Summit. The original discussion on typing tracker is referenced in the PEP draft. -- Ivan
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