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Date: Fri, 5 Apr 2019 12:11:56 +0100
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To: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="000000000000bb20590585c68ee9"
Subject: Re: [PHP-DEV] Question about adding !function_identifier
From: rowan.collins@gmail.com (Rowan Collins)

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On Fri, 5 Apr 2019 at 11:30, Robert Hickman <robehickman@gmail.com> wrote:

> 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.
>


That's an interesting example, but I don't think it generalises as far as
you think: what would a "programmable analyser" do with an array of HTTP
headers, or query-string parameters?

However, I wasn't referring to dynamic *data* like this, but rather dynamic
behaviour in the language itself. A couple of simple examples:

function foo(callable $bar): int { return $bar(); }
function foo(iterable $bar): int { foreach ( $bar as $baz ) { return $baz;
} }

In order to analyse those, you need a) the language to offer a richer type
system (generics, derived types, etc); and b) the programmer to make full
use of that type system, everywhere.

As soon as you have code that's missing rich type information, or use a
truly dynamic feature, that whole section of code becomes essentially
unchecked. That's why Hack is not only adding features for richer
(statically analysed) type annotations, but also *removing* PHP features
which don't work nicely with them.

Regards,
-- 
Rowan Collins
[IMSoP]

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