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In-Reply-To: <becdbf66-be58-4b4e-a0be-52a9c78f7f26@seld.be>
Date: Fri, 22 Mar 2024 11:05:01 +0100
Message-ID: <CAPzBOBObgRg8tdZ_qCrkCtxs56VfJDdYEK27CdfS3DRFZn1Hsw@mail.gmail.com>
Subject: Re: [PHP-DEV] Proposal: AS assertions
To: Jordi Boggiano <j.boggiano@seld.be>
Cc: internals@lists.php.net
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From: landers.robert@gmail.com (Robert Landers)

On Fri, Mar 22, 2024 at 10:31=E2=80=AFAM Jordi Boggiano <j.boggiano@seld.be=
> wrote:
>
> On 2024-03-21 16:02, Robert Landers wrote:
>
> $a as int|float
>
> would be an int, float, or thrown exception.
>
> $a as int|float|null
>
> would be an int, float, or null.
>
> Just a suggestion here which might be more palatable to Rowan's wish for =
consistency (which I can totally relate to):
>
> We perhaps could make sure that as does not throw if used with `??`, or t=
hat `??` catches the type error and returns the right-hand expression inste=
ad:
>
> So to do a nullable typecast you would do:
>
>     $a as int|float ?? null
>
> To me this reads way more intuitive what will happen, and achieves the sa=
me in an also very concise way.
>
> The only catch I see is that it would also swallow errors about $a not be=
ing defined at all.
>
> Best,
> Jordi
>
> --
> Jordi Boggiano
> @seldaek - https://seld.be

Hey Rowan and Jordi,

I did a bit of research into other languages to see how they handle "as":

C#: as never throws, it either returns the type if it can be that type, or =
null
OCaml: fails if an alternative isn't given
Typescript: doesn't actually do anything, just hints the type for the compi=
ler

After asking an AI for some examples and usages, the most compatible
one would be C#'s. In actuality, I think it could be hugely simplified
if we simply return null instead of throwing. There'd be no special
case for |null, and it would move the decision making to the
programmer:

$x =3D $a as int ?? throw new LogicException();

It also still allows for concisely making calls:

$x =3D ($a as MyType)?->doSomething();

What do you think?