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Date: Wed, 27 Jun 2018 09:00:36 +0300
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Subject: RE: [PHP-DEV] [RFC] Deprecate and remove continue targeting switch
From: vsuraski@gmail.com ("Zeev Suraski")

> -----Original Message-----
> From: Nikita Popov [mailto:nikita.ppv@gmail.com]
> Sent: Tuesday, June 26, 2018 9:28 PM
> To: Stanislav Malyshev <smalyshev@gmail.com>
> Cc: PHP internals <internals@lists.php.net>
> Subject: Re: [PHP-DEV] [RFC] Deprecate and remove continue targeting =
switch
>=20
> This RFC resolves the following issue:
>=20
> a) In PHP "switch" is considered a looping structure, for this reason =
"break" and
> "continue" both apply to "switch", as aliases. For PHP, these are =
reasonable
> semantics, as PHP supports multi-level breaks. It would be very =
questionable if
> "break N" and "continue N" could refer to different loop structures =
just because
> there is a "switch" involved somewhere.
>=20
> b) On the other hand, other languages, such as C and C-based =
languages, use a
> different behavior, where "continue" refers to the enclosing loop. As =
these
> languages don't have multi-level breaks, these semantics are also =
reasonable.
>=20
> This leaves us in a position where "continue" means different things =
in PHP and
> in other syntactically similar languages, causing confusing for =
programmers
> familiar with them. This is solved by simply prohibiting the case that =
is
> ambiguous. This is not a loss for PHP developers (who use "break" =
instead of
> "continue" for switch statements anyway), but it is a gain for =
programmers from
> other languages not familiar with this detail (as they get an error =
pointing them
> to one of the correct alternatives).
>=20
> All of this is not a big issue, it's just removing a papercut. IIRC =
this was originally
> motivated by me seeing some bug reports about this behavior.

I think it would be helpful to gauge the levels of these bug reports to =
understand whether it's worth the trouble.

Ultimately - even after this change, C developers won't be able to use =
the C semantics they're used to, as (e.g. in the example in the RFC) - =
'continue;' won't work as they'd expect - and they'd have to acquaint =
themselves with 'continue 2;'.  It's true that if we 'force' them to =
acquaint themselves with multi-level loop control structures there's =
reduced 'continue;' erroneously.  But unless this is really A Thing, as =
in, something pretty common - I think the mess involved with forcing =
people who have working code to try and (a) understand the change, and =
(b) understand their (potentially quite ancient) code flows may outweigh =
the benefits.

Zeev