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Date: Wed, 18 Feb 2015 11:14:04 +0200
Message-ID: <CAPhkiZxvJda-Q1WEr7LTrX9BCHKs0QapQ8f=hh8L+1SNC+KFHQ@mail.gmail.com>
To: Zeev Suraski <zeev@zend.com>
Cc: Nikita Popov <nikita.ppv@gmail.com>, Rasmus Lerdorf <rasmus@lerdorf.com>, 
	Sara Golemon <pollita@php.net>, PHP internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] Scalar Type Hints v0.4
From: narf@devilix.net (Andrey Andreev)

Hi,

On Wed, Feb 18, 2015 at 9:00 AM, Zeev Suraski <zeev@zend.com> wrote:
>> -----Original Message-----
>> From: Nikita Popov [mailto:nikita.ppv@gmail.com]
>> Sent: Wednesday, February 18, 2015 3:06 AM
>> To: Rasmus Lerdorf
>> Cc: Sara Golemon; PHP internals
>> Subject: Re: [PHP-DEV] Scalar Type Hints v0.4
>>
>> The inability to implicitly cast "123" to int is pretty much the KEY
>> distinction
>> between weak and strict scalar typehints (those pesky value-dependent type
>> checks). If the strict typing mode doesn't offer this, what's the point at
>> all?
>
> I am wondering what the point is indeed with preventing "123" to 123.  So
> far, all the concrete use cases people brought up had to do with "Apple" or
> "100 dogs", but nobody ever seems to be able to explain why converting "123"
> to 123 is likely to be a problem real world.  Is it really just static
> analyzers?
>

I too am curious about the potential issue with "123" to 123
specifically, although it could be seen as a subset of another problem
that is solved with strict hints - numeric-character string
identifiers being erroneously treated as integers.

That is especially bad when such identifiers are in fact generated as
integers first so that they are incremental, but the
program/database/business logic requires them to be fixed-length
strings and/or in hexadecimal format. In such cases, even silently
discarding leading zeros can prove to be problematic, while in the
case of hexadecimal representations you'd need more than 10 data
samples to notice the problem if you don't use a strict hint.
Obviously, that would be solved with automated testing, but
unfortunately even code with high test coverage % often lacks depth in
its test cases.

I believe reduced amount of necessary unit tests was already brought
up as an advantage of strict type hints, so I'm just explaining one
such use case in detail here.

Cheers,
Andrey.