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Date: Tue, 17 Feb 2015 08:38:48 -0800
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To: Rasmus Lerdorf <rasmus@lerdorf.com>
Cc: francois@php.net, Philip Sturgeon <pjsturgeon@gmail.com>, 
	Arvids Godjuks <arvids.godjuks@gmail.com>, Jefferson Gonzalez <jgmdev@gmail.com>, 
	Rowan Collins <rowan.collins@gmail.com>, PHP internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] Reviving scalar type hints
From: pollita@php.net (Sara Golemon)

On Tue, Feb 17, 2015 at 12:22 AM, Rasmus Lerdorf <rasmus@lerdorf.com> wrote:
> On 02/16/2015 09:48 PM, Sara Golemon wrote:
>> Second, I should clarify that while the HHVM runtime performs
>> coersion, the hack type checker is strict.  So my original statement
>> was inaccurate.  As far as hack is concerned, it's simply strict.
>> Period.
>
> With both the default (partial) type checking and strict enabled, my
> number_format() example in Hack produces:
>
> ...
>
> Please correct me here if I somehow ran these incorrectly. I did put
> some deliberate type errors into my userspace code and hh_client caught
> those nicely, so it seems like it was working, but it didn't catch
> anything when it came to calling the internal API functions.
>
The mechanisms are strict, but the definitions, in hack, are untyped,
so there's nothing to validate:

hphp/hack/hhi/stdlib/builtins_string.hhi:
  function number_format($number, $decimals = 0, $dec_point = ".",
$thousands_sep = ",");

We left a lot of stuff untyped from hack's point of view precisely
because so much of PHP's APIs are non-sensical.  Have you looked at
what chr() does with bad types lately? Yikes.

> So, you keep asking what I would support. I would like to see an RFC
> along the following lines:
>
> 1. Tighten up the type coercion for the "1000 dogs" case although we
>    have to look at whether there is a problem with some database APIs
>    returning space-padded fields so "1000    " would now break.
>    Hopefully that is fringe enough to not break the world.
>
Hopefully, though I think that we could embrace the idea of trailing
space as insignificant.

> 2a. In strict mode, tone down the strictness and allow non-lossy
>     coercion including int->float. And yes, I know in really edge cases
>     that isn't technically non-lossy, but for all practical purposes it
>     is.
>
Nod. Ze'ev called for this too.

> 2b. A much more flexible system for specifying multiple types. I should
>     be able to say that my function takes something that looks like a
>     number if I choose and still take advantage of stricter typing for
>     other parameters.
>
Union types.  I'm hear a lot of support for this concept, and not
exclusively from one camp.
Perhaps with a psuedo-type defined somewhere to account for the
half-type "numeric string".

> 3. Don't turn on crazy-strict mode for internal functions that weren't
>    designed for that. Instead provide the same ability as userspace gets
>    for developers to gradually design their APIs to be stricter if they
>    so desire allowing both Hack and PHP to implement a stricter
>    curl_setopt(), for example.
>
Perhaps a ZEND_ACC_STRICT flag which lets an API opt-in to strict mode?
Or something passed to the arg_info struct? The details are secondary,
but you get my meaning...

-Sara