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Date: Fri, 22 Mar 2024 17:46:27 +0000
To: "Claude Pache" <claude.pache@gmail.com>
Cc: internals@lists.php.net
Subject: Re: [PHP-DEV] Proposal: AS assertions
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

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On Fri, 22 Mar 2024, at 17:38, Claude Pache wrote:
>=20
>> Le 22 mars 2024 =C3=A0 16:18, Rowan Tommins [IMSoP] <imsop.php@rwec.c=
o.uk> a =C3=A9crit :
>>=20
>> $optionalExpiryDateTime =3D $expiry as ?DateTimeInterface else some_o=
ther_function($expiry);
>> assert($optionalExpiryDateTime is ?DateTimeInterface); // cannot fail=
, already asserted by the "as"
>=20
> I think that the `is` operator is all we need; the `as` operator adds =
syntax complexity for little gain. Compare:
>=20
> $optionalExpiryDateTime =3D $expiry as ?DateTimeInterface else some_ot=
her_function($expiry);
>=20
> vs
>=20
> $optionalExpiryDateTime =3D $expiry is ?DateTimeInterface ? $expiry : =
some_other_function($expiry);


I agree, it doesn't add much; and that's what the draft RFC Ilija linked=
 to says as well.

But the point of that particular example is that after the "is" version,=
 you don't actually know the type of $optionalExpiryDateTime without loo=
king up the return type of some_other_function()

With the "as" version, you can see at a glance that after that line, $op=
tionalExpiryDateTime is *guaranteed* to be DateTimeInterface or null, wh=
ich I understood to be the intention of Robert's original proposal on th=
is thread.

--=20
Rowan Tommins
[IMSoP]

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<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}</style></head><body><div>On Fri, 22 Mar =
2024, at 17:38, Claude Pache wrote:<br></div><blockquote type=3D"cite" i=
d=3D"qt" style=3D"overflow-wrap:break-word;"><div><br></div><div><blockq=
uote type=3D"cite"><div>Le 22 mars 2024 =C3=A0 16:18, Rowan Tommins [IMS=
oP] &lt;imsop.php@rwec.co.uk&gt; a =C3=A9crit :<br></div><div><br></div>=
<div><div><span style=3D"font-style:normal;font-variant-caps:normal;font=
-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-=
transform:none;text-wrap-mode:wrap;word-spacing:0px;-webkit-text-stroke-=
width:0px;text-decoration-line:none;text-decoration-style:solid;text-dec=
oration-color:currentcolor;text-decoration-thickness:auto;float:none;dis=
play:inline !important;"><span class=3D"font" style=3D"font-family:Helve=
tica;"><span class=3D"size" style=3D"font-size:14px;">$optionalExpiryDat=
eTime =3D $expiry as ?DateTimeInterface else some_other_function($expiry=
);</span></span></span><br></div><div><span style=3D"font-style:normal;f=
ont-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align=
:start;text-indent:0px;text-transform:none;text-wrap-mode:wrap;word-spac=
ing:0px;-webkit-text-stroke-width:0px;text-decoration-line:none;text-dec=
oration-style:solid;text-decoration-color:currentcolor;text-decoration-t=
hickness:auto;float:none;display:inline !important;"><span class=3D"font=
" style=3D"font-family:Helvetica;"><span class=3D"size" style=3D"font-si=
ze:14px;">assert($optionalExpiryDateTime is ?DateTimeInterface); // cann=
ot fail, already asserted by the "as"</span></span></span><br></div></di=
v></blockquote></div><div><br></div><div>I think that the `is` operator =
is all we need; the `as` operator adds syntax complexity for little gain=
. Compare:<br></div><div><br></div><div>$optionalExpiryDateTime =3D $exp=
iry as ?DateTimeInterface else some_other_function($expiry);<br></div><d=
iv><br></div><div>vs<br></div><div><br></div><div>$optionalExpiryDateTim=
e =3D $expiry is ?DateTimeInterface ? $expiry : some_other_function($exp=
iry);<br></div></blockquote><div><br></div><div><br></div><div>I agree, =
it doesn't add much; and that's what the draft RFC Ilija linked to says =
as well.<br></div><div><br></div><div>But the point of that particular e=
xample is that after the "is" version, you don't actually know the type =
of $optionalExpiryDateTime without looking up the return type of some_ot=
her_function()<br></div><div><br></div><div>With the "as" version, you c=
an see at a glance that after that line, $optionalExpiryDateTime is *gua=
ranteed* to be DateTimeInterface or null, which I understood to be the i=
ntention of Robert's original proposal on this thread.<br></div><div><br=
></div><div>-- <br></div><div>Rowan Tommins<br></div><div>[IMSoP]<br></d=
iv><div><br></div></body></html>
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