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Date: Wed, 4 Apr 2012 10:29:12 +0800
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To: Alan Knowles <alan@akbkhome.com>
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Subject: Re: [PHP-DEV] Catchable - marking methods just like static?
From: aharvey@php.net (Adam Harvey)

On 4 April 2012 10:02, Alan Knowles <alan@akbkhome.com> wrote:
> PHP enforces rules like $this can not be used in a method marked 'static'=
.
> So why not flag methods (and internal functions) with a flag that indicat=
es
> they can throw things. Since PHP is not a compiled language we can not pi=
ck
> up 'all' of the potential scenarios, but even if E_NOTICE's pick up 80% i=
t
> would make code considerably more maintainable.

I don't like this. It's basically the equivalent of Java's "throws
Exception" antipattern[0] with none of the claimed benefits of
checked, fine grained exception specification (which I'm dubious about
in general, particularly having also used C++'s static exception
specifiers, which are even worse than Java's dynamic ones).

There are issues with both backward and forward compatibility here:
assuming this was in PHP 5.5, you could effectively no longer write
code that was E_STRICT/E_NOTICE clean in both PHP 5.4 and 5.5 =E2=80=94=C2=
=A0you
can't add catchable to functions in PHP 5.4 because it's not a
keyword, but you can't throw an exception in PHP 5.5 without it unless
you're prepared to incur a notice. And the associated performance
loss, which may turn out to be significant if it's happening on most
function calls in a script's lifetime.

Also, I already know how to use exceptions, and write clean code. I
don't really want to have to add catchable to all of the functions
I've written that may throw =E2=80=94=C2=A0or may call library functions th=
at may
throw =E2=80=94=C2=A0when I upgrade to PHP 5.5. It's a lot of work, and giv=
en that
a lot of libraries now use exceptions, a lot of developers would end
up almost mechanically adding catchable to pretty much every function,
which loses any minimal code quality advantage that might exist.

Exception specifications in general don't feel very PHPish to me, but
that would be a different discussion. Catchable, as a limited form of
exception specification, feels even less useful than that.

> Anyway... flame away ;)

Sorry, I guess I kind of did. It's nothing personal. :)

Adam

[0] http://today.java.net/article/2006/04/04/exception-handling-antipattern=
s#throwingException