[Python-Dev] Do PEP 526 type declarations define the types of variables or not?

[Nick Coghlan]

On 7 September 2016 at 01:33, Ivan Levkivskyi <levkivskyi at gmail.com> wrote:
> On 6 September 2016 at 17:25, Mark Shannon <mark at hotpy.org> wrote:
>>
>> The issue is not whether the checker can tell that the type of the
>> *expression* is int, but whether it is forced to use the type of the
>> *variable*. The current wording of PEP 526 strongly implies the latter.
>
> Mark,
> Could you please point to exact locations in the PEP text and propose an
> alternative wording, so that we will have a more concrete discussion.

Rather than trying to work that out on the list, it may make the most
sense for Mark to put together a PR that rewords the parts of the PEP
that he sees as constraining typecheckers to restrict *usage* of a
variable based on its annotation, rather than just restricting future
bindings to it.

It seems to me everyone's actually in pretty good agreement on how we
want variable annotations to work (constraining future assignments to
abide by the declaration, without constraining use when inference
indicates a more specific type), but the PEP may be using some
particular terminology more loosely than is strictly correct in the
context of type theory.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia