syntax difference

[Jim Lee]

On 06/18/2018 11:01 AM, Ian Kelly wrote:
> On Mon, Jun 18, 2018 at 11:39 AM Jim Lee <jlee54 at gmail.com> wrote:
>> On 06/18/2018 07:03 AM, Steven D'Aprano wrote:
>>> As a human programmer, you surely perform your own ad hoc type checking
>>> when you write and debug code.
>> Of course.  And, I use linting tools and other forms of static type
>> checking.  What I don't like is adding the *syntax* for static type
>> checking to the (dynamically typed) language proper, particularly when
>> the implementations of said language do nothing but ignore it.
>>
>> The syntax should be defined inside comments, by the tools that actually
>> need to use them.  Let the tools do what they were designed to do.  Let
>> the language do what it was designed to do.
> If you want to use a type checking tool that uses type comments, then
> by all means do so. The existence of annotation syntax in no way
> prevents that.
No, but it adds an awful lot of functionally inert noise to live code.
> When PEP 3107 was written, it was anticipated that annotations would
> find more uses than just type hinting. Some of those proposed ideas
> (e.g. database query mapping) depend on the annotation being readable
> at run-time, for which a comment would be wholly inadequate. In
> practice, I don't think that has really been borne out. Still, the
> intention was to make the language more flexible, not just to cram in
> type hinting, and I don't think that was necessarily a bad idea.
>
> PEP 484 was created out of the observation that the community of
> static type analysis tools that has grown out of PEP 3107 would
> benefit from a common dialect of types. All it does is provide that.
>
> Neither of these are forcing you to use a type checker that requires
> annotations for type hints rather than comments, if that's what you
> prefer. The annotation-based checker is probably a fair bit easier to
> build from the maintainer's standpoint, though, since it can rely on
> existing parsing tools and the typing module.
Thanks for the explanation, but it only reinforces my view.  The more 
entrenched this feature becomes, the more we will see annotation-based 
tools and, at some point, we will all be forced to used annotations in 
order to take advantage of the tools.

-Jim