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Date: Sat, 05 Dec 2020 08:42:44 -0600
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Subject: Re: [PHP-DEV] [RFC] Enumerations
From: larry@garfieldtech.com ("Larry Garfield")

On Sat, Dec 5, 2020, at 3:26 AM, Pierre R. wrote:
> Le 05/12/2020 =C3=A0 00:24, Larry Garfield a =C3=A9crit=C2=A0:
> > Greetings, denizens of Internals!
> >
> > Ilija Tovilo and I have been working for the last few months on addi=
ng 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 st=
age, unit enumerations, are just about ready for public review and discu=
ssion.
> >
> > 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 st=
art a discussion on and get broader feedback on the outstanding nits.
> >
> > I should note that while the design has been collaborative, credit f=
or the implementation goes entirely to Ilija.  Blame for any typos in th=
e RFC itself go entirely to me.
> >
> > *dons flame-retardant suit*
> >
> Another question, about match() behavior:
>=20
>  > This usage requires no modification of |match|. It is a natural=20
> implication of the current functionality.
>=20
> May be this could be the time to have a "strict match", using enums, w=
e=20
> can "statically" guess if branches are missing (of course, whenever yo=
u=20
> use default it valid to miss branches) - one thing I'd love is PHP to=20=

> throw a fatal error when compiling a match expression whose missing=20=

> branches, and not wait until runtime to fail.

I think that would make a great follow-up, but it's out of scope for now=
.  Having match statically know what the available types are when the va=
riable type isn't yet known (because it's in another file) is... I don't=
 know how to do that.  That's a broad problem across PHP, frankly.  If w=
e can figure out a way to do so, I'd support adding it in the future.  (=
I can't speak for Ilija, but I suspect he would be on board as well.)

--Larry Garfield