[Python-Dev] What should a good type checker do? (was: Please reject or postpone PEP 526)

[Koos Zevenhoven]

What's up with the weird subthreads, Stephen?!

On Guido's suggestion, I'm working on posting those type-checking thoughts here.

-- Koos

On Sat, Sep 3, 2016 at 6:17 PM, Stephen J. Turnbull
<turnbull.stephen.fw at u.tsukuba.ac.jp> wrote:
> Please respect Reply-To, set to python-ideas.
>
> Greg Ewing writes:
>  > Chris Angelico wrote:
>  > > Forcing people to write 1.0 just to be compatible with 1.5 will cause
>  > > a lot of annoyance.
>  >
>  > Indeed, this would be unacceptable IMO.
>
> But "forcing" won't happen.  Just ignore the warning.  *All* such
> Python programs will continue to run (or crash) exactly as if the type
> declarations weren't there.  If you don't like the warning, either
> don't run the typechecker, or change your code to placate it.
>
> But allowing escapes from a typechecker means allowing escapes.  All
> of them, not just the ones you or I have preapproved.  I want my
> typechecker to be paranoid, and loud about it.
>
> That doesn't mean I would never use a type like "Floatable" (ie, any
> type subject to implicit conversion to float).  But in the original
> example, I would probably placate the typechecker.  YMMV, of course.
>
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-- 
+ Koos Zevenhoven + http://twitter.com/k7hoven +