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Date: Sat, 05 Dec 2020 14:26:43 -0600
To: "php internals" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Enumerations
From: larry@garfieldtech.com ("Larry Garfield")

On Fri, Dec 4, 2020, at 5:24 PM, Larry Garfield wrote:
> Greetings, denizens of Internals!
> 
> Ilija Tovilo and I have been working for the last few months on adding 
> support for enumerations and algebraic data types to PHP.  This is a 
> not-small task, so we've broken it up into several stages.  The first 
> stage, unit enumerations, are just about ready for public review and 
> discussion.
> 
> The overarching plan (for context, NOT the thing to comment on right 
> now) is here: https://wiki.php.net/rfc/adts
> 
> The first step, for unit enumerations, is here:
> 
> https://wiki.php.net/rfc/enumerations
> 
> There's still a few bits we're sorting out and the implementation is 
> mostly done, but not 100% complete.  Still, it's far enough along to 
> start a discussion on and get broader feedback on the outstanding nits.
> 
> I should note that while the design has been collaborative, credit for 
> the implementation goes entirely to Ilija.  Blame for any typos in the 
> RFC itself go entirely to me.
> 
> *dons flame-retardant suit*
> 
> -- 
>   Larry Garfield
>   larry@garfieldtech.com

Thank you everyone for the feedback so far!  I've updated the RFC with a few changes, based on discussion here and elsewhere:

* Clarified that "enums behave like objects unless otherwise specified."  That should clarify a lot of edge case questions.  (Which is specifically one of the reasons to build off of objects.  We can inherit answers to most edge cases.)
* Primitive-backed Cases have been renamed to Scalar Enums, because "Primitive-backed" is just too clumsy to say or write all the time.
* There's now formal internal interfaces defined for Enum, UnitEnum, and ScalarEnum to define the methods mentioned.  These serve as both documentation and to allow user-space code to tell when a value it's dealing with is an enum, and a particular type of enum.  (And therefore what enum methods are available.)
* Added a value() method to ScalarEnum, to make it easier to get at the scalar equivalent arbitrarily.
* Fixed a bunch of typos.
* Updated the reflection section to have getType() return a ReflectionType rather than a bare string.

(The patch will be updated for the above shortly as Ilija's time allows.)

--Larry Garfield