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Date: Thu, 17 Sep 2015 19:52:28 -0400
Cc: Rowan Collins <rowan.collins@gmail.com>, internals@lists.php.net
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To: Bob Weinand <bobwei9@hotmail.com>
Subject: Re: [PHP-DEV] Let's discuss enums!
From: jbafford@zort.net (John Bafford)

On Sep 17, 2015, at 19:16, Bob Weinand <bobwei9@hotmail.com> wrote:
>=20
>> Am 18.09.2015 um 01:06 schrieb Rowan Collins =
<rowan.collins@gmail.com>:
>>=20
>> This has come up in passing a few times recently, but I'm not sure =
there's ever been a dedicated discussion of it: would it be useful for =
PHP to have a built-in Enumeration type, and if so, how should it look?
>=20
> I like enums in general, but I'd like to note that there's already a =
RFC in draft by Levi:
>=20
> https://wiki.php.net/rfc/enum <https://wiki.php.net/rfc/enum>
>=20
> As far as I know, the RFC is already fairly final and just lacks an =
implementation.
>=20
> So, I'd consider bikeshedding an actual RFC first.


If we=E2=80=99re bikeshedding, one feature I would really like to see, =
with typehinting, is warnings if all cases of an enum aren=E2=80=99t =
handled in a switch. So, for example, given our example Weekdays enum, =
if I wrote this code:

switch(Weekday $someWeekday) {
	case Weekday::MONDAY: break;
	case Weekday::TUESDAY: break;
}

By providing the typehint, I=E2=80=99m indicating that I want to get a =
warning/error that the switch does not cover all enum values. This would =
be very handy if an enum value is added after initial development and =
someone misses a switch statement in cleanup.

The typehint would also allow generating a warning if someone did =
something like

switch(Weekday $someWeekday) {
	//case =E2=80=A6 all the weekdays: break;
	case =E2=80=98I am not a Weekday=E2=80=99: echo =E2=80=98Generate =
a fatal error here because string is not a Weekday.=E2=80=99;
}

-John