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Date: Mon, 03 Feb 2025 19:44:21 +0100
To: "Dmitry Derepko" <xepozzd@gmail.com>,
 "Rob Landers" <landers.robert@gmail.com>
Cc: internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Re: Discussion: making continue and break into an expression
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From: rob@bottled.codes ("Rob Landers")

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On Sun, Feb 2, 2025, at 14:35, Dmitry Derepko wrote:
>=20
>> On Jan 25, 2024, at 12:16=E2=80=AFPM, Robert Landers <landers.robert@=
gmail.com> wrote:
>>=20
>> Hello internals,
>>=20
>> Now that throwing is an expression, it allows for some very concise
>> programming. What are your thoughts on making a break/continue into an
>> expression as well?
>=20
> Hi!=20
> I had similar idea to make `break`, `continue` and `return` be express=
ions instead of statements to simplify almost the same cases as Robert d=
escribed above.
>=20
> Grammar corrections in the PR. https://github.com/php/php-src/pull/176=
47=20
> Ilija pointed to memory leaking problems as well.
>=20
> Thinking about Ilija memory leaking case:
> new Foo + return 1
>=20
> I think we may have a workaround here, by allowing all of these constr=
uctions only available at some specific points:
> - <point> as the statement now
> - $cond ? <point> : <point>;
> - match ($v) { =E2=80=A6 =3D> <point> }
>=20
> So it will deny such cases:
> - operand OPERATOR <point> (1 + return; $cond && break; etc)
>=20
> It may prevent memory leaking problems. Isn=E2=80=99t it?
>=20
> I=E2=80=99m writing RFC: https://wiki.php.net/rfc/return_break_continu=
e_expressions=20
> I=E2=80=99ll start a new discussion when it will be ready for it.
>=20
>=20
> ----------
>=20
> Best regards,
> Dmitrii Derepko.
> @xepozz

Oh, this was a fun one!

I ended up rewriting the AST during compilation (pass 2) to return/break=
 on the next statement instead of in the current statement. That let me =
get around the issue but I guessed nobody would like it and it probably =
wouldn=E2=80=99t pass on technical reasons.

In other words, yes it was an expression on the grammar level, but it wa=
s compiled as a statement.

=E2=80=94 Rob
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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 Sun, Feb 2, =
2025, at 14:35, Dmitry Derepko wrote:<br></div><blockquote type=3D"cite"=
 id=3D"qt" style=3D"overflow-wrap:break-word;line-break:after-white-spac=
e;"><div><div><div><br></div></div><div><blockquote type=3D"cite"><div>O=
n Jan 25, 2024, at 12:16=E2=80=AFPM, Robert Landers &lt;landers.robert@g=
mail.com&gt; wrote:<br></div><div><br></div><div><div><div>Hello interna=
ls,<br></div><div><br></div><div>Now that throwing is an expression, it =
allows for some very concise<br></div><div>programming. What are your th=
oughts on making a break/continue into an<br></div><div>expression as we=
ll?<br></div></div></div></blockquote></div><div><br></div><div><div>Hi!=
&nbsp;<br></div><div>I had similar idea to make `break`, `continue` and =
`return` be expressions instead of statements to simplify almost the sam=
e cases as Robert described above.<br></div><div><br></div><div>Grammar =
corrections in the PR.&nbsp;<a href=3D"https://github.com/php/php-src/pu=
ll/17647">https://github.com/php/php-src/pull/17647</a>&nbsp;<br></div><=
div>Ilija pointed to memory leaking problems as well.<br></div><div><br>=
</div><div>Thinking about Ilija memory leaking case:<br></div><div>new F=
oo + return 1<br></div><div><br></div><div>I think we may have a workaro=
und here, by allowing all of these constructions only available at some =
specific points:<br></div><div>- &lt;point&gt; as the statement now<br><=
/div><div>- $cond ? &lt;point&gt; : &lt;point&gt;;<br></div><div>- match=
 ($v) { =E2=80=A6 =3D&gt; &lt;point&gt; }<br></div><div><br></div><div>S=
o it will deny such cases:<br></div><div>- operand OPERATOR &lt;point&gt=
; (1 + return; $cond &amp;&amp; break; etc)<br></div><div><br></div><div=
>It may prevent memory leaking problems. Isn=E2=80=99t it?<br></div><div=
><br></div><div>I=E2=80=99m writing RFC:&nbsp;<a href=3D"https://wiki.ph=
p.net/rfc/return_break_continue_expressions">https://wiki.php.net/rfc/re=
turn_break_continue_expressions</a>&nbsp;<br></div><div>I=E2=80=99ll sta=
rt a new discussion when it will be ready for it.<br></div><div><div><br=
></div><div><div><div><br></div><div>----------<br></div><div><br></div>=
<div>Best regards,<br></div><div>Dmitrii Derepko.<br></div><div>@xepozz<=
br></div></div></div></div></div></div></blockquote><div><br></div><div>=
Oh, this was a fun one!<br></div><div><br></div><div>I ended up rewritin=
g the AST during compilation (pass 2) to return/break on the next statem=
ent instead of in the current statement. That let me get around the issu=
e but I guessed nobody would like it and it probably wouldn=E2=80=99t pa=
ss on technical reasons.<br></div><div><br></div><div>In other words, ye=
s it was an expression on the grammar level, but it was compiled as a st=
atement.</div><div><br></div><div id=3D"sig121229152">=E2=80=94 Rob<br><=
/div></body></html>
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