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Date: Tue, 25 Jun 2024 09:44:34 +0200
Message-ID: <CAAX=eQNtGbfGA_wXbG=6Fe_6Hemu+O1JAjM3fzS_4egBuY_yMg@mail.gmail.com>
Subject: Re: [PHP-DEV] Add $this return type
To: radar3301 <radar3301@gmail.com>
Cc: internals@lists.php.net
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From: cardamoneluigi@gmail.com (Luigi Cardamone)

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On Tue, Jun 25, 2024 at 2:29=E2=80=AFAM radar3301 <radar3301@gmail.com> wro=
te:

> I'm looking for initial feedback on the following proposal.
>
> Often, we have the following (fluent interface) setter method:
>
> public function setName(?string $name): static
> {
>     $this->name =3D $name;
>
>     return $this;
> }
>
> I propose to add "$this" as a return type, ie:
>
> public function setName(?string $name): $this
> {
>     $this->name =3D $name;
>     // implicit return $this;
> }
>
> public function setName(?string $name): $this
> {
>     $this->name =3D $name;
>     // this would be an (compiler?) error
>     return $somethingOtherThanThis;
> }
>
> public function setName(?string $name): $this
> {
>     $this->name =3D $name;
>     $self =3D $this;
>     // this would not be an error
>     return $self;
> }
>
> public function setName(?string $name): $this
> {
>     $this->name =3D $name;
>     // technically useless, but not an error
>     return $this;
> }
>
> public function setName(?string $name): $this
> {
>     $this->name =3D $name;
>     if ('foobar' =3D=3D=3D $name) {
>         // not an error to return early
>         return;
>     }
>     // do some other stuff
>
>     // any of the above legal examples
> }
>
> It should be obvious, but functions outside of a class context would not
> be able to use this syntax.
>
> BC:
> There would be no BC breaks, as this syntax is currently invalid (Parse
> error: syntax error, unexpected variable "$this").
>
> Other Considerations:
> With regards to reflection and inheritance, "$this" would be considered a=
n
> alias for "static".
>
> Regards,
> radar3301
>

I strongly agree that an alias for the "static" keyword is really necessary
to improve the semantics of the language.
The word "static" is used for many things: static methods, static classes
and Late Static Bindings (that is the case that you are discussing).

I think that in the case of Late Static Bindings (e.g. `new static()` or
return type `..(): static`), the word "static" does not give any clue about
the meaning of that code.
Thus, I like your proposal.

The part that I do not like is the implicit return: it may confuse
developers and static analysis tools.

Is it possible to replace "$this" with "this"? Cleaner and coherent with
"self".

Regards,
Luigi

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Tue, Jun 25, 2024 at 2:29=E2=80=AF=
AM radar3301 &lt;<a href=3D"mailto:radar3301@gmail.com">radar3301@gmail.com=
</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:=
0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">=
<div dir=3D"ltr"><div>I&#39;m looking for initial feedback on the following=
 proposal.</div><div><br></div>Often, we have the following=C2=A0(fluent in=
terface) setter method:<br><br><div>public function setName(?string $name):=
 static</div><div>{<br>=C2=A0 =C2=A0 $this-&gt;name =3D $name;<br><br>=C2=
=A0 =C2=A0 return $this;<br>}</div><div><br></div><div>I propose to add &qu=
ot;$this&quot; as a return type, ie:</div><div><br>public function setName(=
?string $name): $this</div><div>{<br>=C2=A0 =C2=A0 $this-&gt;name =3D $name=
;</div><div>=C2=A0 =C2=A0 // implicit return $this;</div><div>}</div><div><=
br></div><div>public function setName(?string $name): $this<br></div><div>{=
<br>=C2=A0 =C2=A0 $this-&gt;name =3D $name;</div><div>=C2=A0 =C2=A0 // this=
 would be an (compiler?) error</div><div>=C2=A0 =C2=A0 return $somethingOth=
erThanThis;</div><div>}</div><div><br>public function setName(?string $name=
): $this<br></div><div>{<br>=C2=A0 =C2=A0 $this-&gt;name =3D $name;<br>=C2=
=A0 =C2=A0 $self =3D $this;</div><div>=C2=A0 =C2=A0 // this would not be an=
 error</div><div>=C2=A0 =C2=A0 return $self;</div><div>}</div><div><br>publ=
ic function setName(?string $name): $this<br></div><div>{<br>=C2=A0 =C2=A0 =
$this-&gt;name =3D $name;</div><div>=C2=A0 =C2=A0 // technically useless, b=
ut not an error</div><div>=C2=A0 =C2=A0 return $this;</div><div>}</div><div=
><br>public function setName(?string $name): $this<br></div><div>{<br>=C2=
=A0 =C2=A0 $this-&gt;name =3D $name;</div><div>=C2=A0 =C2=A0 if (&#39;fooba=
r&#39; =3D=3D=3D $name) {</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 // not an e=
rror to return early</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 return;</div><di=
v>=C2=A0 =C2=A0 }</div><div>=C2=A0 =C2=A0 // do some other stuff</div><div>=
<br>=C2=A0 =C2=A0 // any of the above legal examples</div><div>}</div><div>=
<br></div><div>It should be obvious, but functions outside of a class conte=
xt would not be able to use this syntax.</div><div><br></div><div>BC:</div>=
<div>There would be no BC breaks, as this syntax is currently invalid (Pars=
e error: syntax error, unexpected variable &quot;$this&quot;).</div><div><b=
r></div><div>Other Considerations:</div><div>With regards to reflection and=
 inheritance, &quot;$this&quot; would be considered an alias for &quot;stat=
ic&quot;.</div><div><br></div><div>Regards,</div><div>radar3301</div></div>=
</blockquote><div><br></div><div>I strongly agree that an alias for the &qu=
ot;static&quot; keyword is really necessary to improve the semantics of the=
 language. <br></div><div>The word &quot;static&quot; is used for many thin=
gs: static methods, static classes and Late Static Bindings (that is the ca=
se that you are discussing).</div><div><br></div><div>I think that in the c=
ase of Late Static Bindings (e.g. `new static()` or return type `..(): stat=
ic`), the word &quot;static&quot; does not give any clue about</div><div>th=
e meaning of that code.</div><div>Thus, I like your proposal.</div><div><br=
></div><div>The part that I do not like is the implicit return: it may conf=
use developers and static analysis tools.</div><div><br></div><div>Is it po=
ssible to replace &quot;$this&quot; with &quot;this&quot;? Cleaner and cohe=
rent with &quot;self&quot;.</div><div><br></div><div>Regards,<br></div><div=
>Luigi<br></div><div><br></div><div><br></div></div></div>

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