[Python-Dev] Re: PEP 647 (type guards) -- final call for comments

On 2/14/21 2:34 PM, Guido van Rossum wrote:

On Sun, Feb 14, 2021 at 12:51 PM David Mertz <mertz@gnosis.cx mailto:mertz@gnosis.cx> wrote:

On Sun, Feb 14, 2021, 2:53 PM Gregory P. Smith <greg@krypto.org
<mailto:greg@krypto.org>> wrote:

    *TL;DR of my TL;DR* - Not conveying bool-ness directly in the
    return annotation is my only complaint.  A BoolTypeGuard
    spelling would alleviate that.


This is exactly my feeling as well. In fact, I do not understand
why it cannot simply be a parameterized Bool. That would avoid all
confusion. Yes, it's not the technical jargon type system
designers use... But the existing proposal moves all the mental
effort to non-experts who may never use type checking tools.

But note that 'bool' in Python is not subclassable.

No, but this hypothetical 'Bool'--presumably added to typing.py--might well be.

Cheers,

//arry/