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In-Reply-To: <CALKiJKqF8vgOik8aRc8_dm=Y+o58NqA3PoYvpf7XZcXs55831A@mail.gmail.com>
Date: Fri, 5 Apr 2019 11:30:37 +0100
Message-ID: <CAMuFt-7mYgBG02SegZTMm2j728DcojSiaG0JRAJVE23ioU0Ryg@mail.gmail.com>
To: Rowan Collins <rowan.collins@gmail.com>
Cc: PHP internals <internals@lists.php.net>
Content-Type: text/plain; charset="UTF-8"
Subject: Re: [PHP-DEV] Question about adding !function_identifier
From: robehickman@gmail.com (Robert Hickman)

>
> The tricky part is that PHP is a highly dynamic language, so there's a lot
> of cases where the analysis can only return "maybe". My understanding is
> that this is what a lot of the work on Hack is doing: creating a language
> which looks a lot like PHP, but doesn't have as many ambiguous cases which
> can't be analysed statically.
>

Quite a lot of code that apparently cannot be statically analysed
could be if the static analyser was programmable. To give a simple
example:

$result = mysqli_query ($conn, 'select * from some_table');
$arr = mysqli_fetch_assoc ($result);

The contents of '$arr' cannot be known using only the data provided in
this code, however it's contents is statically knowable. If a static
analyser were programmable, it could parse the SQL query and query the
database to find out what keys exist in some_table. Thus it could
check for references to non-existing keys.

I suspect this is the case for a lot of 'non analysable code', it can
only function within a known set of states, but the type system is
unaware of those states.