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Date: Fri, 06 Sep 2024 18:34:52 -0500
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Subject: Re: [PHP-DEV] bikeshed: Typed Aliases
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From: larry@garfieldtech.com ("Larry Garfield")

On Fri, Sep 6, 2024, at 6:27 PM, Rob Landers wrote:

>> I suspect there's also other edge case bits to worry about, particula=
rly if trying to combine a complex alias with a complex type, which coul=
d lead to violating the DNF rule.  For example:
>
> Oh, DNF is the bane of my existence with this RFC=E2=80=94I don't want=
 to mess=20
> this up. I'll see you at the end of the example, though.
>
>>=20
>> typealias Foo: (Bar&Baz)|Beep;
>>=20
>> use (Bar&Baz)|Beep as Foo;
>>=20
>> function narf(Foo&Stringable $s) {}
>>=20
>> With the compile time approach, that would expand to `(Bar&Baz)|Beep&=
Stringable`, which is not a valid type def.
>
> I can see how you arrived at this, but I think you may have missed a=20
> step, since the entirety of Foo will be &'d with Stringable.
>
> Foo =3D (Bar & Baz) | Beep
>
> want: (Foo) & Stringable
>
> expand Foo: ((Bar & Baz) | Beep) & Stringable
>
> Which can be reduced to the following in proper DNF (at least, it=20
> compiles=E2=80=94https://3v4l.org/0bMlP):
>
> (Beep & Stringable) | (Bar & Baz & Stringable)
>
> It's probably a good idea to update the RFC explaining how expansion w=
orks.

Woof.  We're not "fixingup" anyone's DNF elsewhere.  I cannot speak for =
everyone, but I'd be perfectly fine not doing any magic fixing for now, =
and then debating separately if we should do it more generally.  Just do=
ing it for aliases doesn't seem like the best plan.

--Larry Garfield