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Date: Mon, 24 Jun 2024 18:25:26 -0600
Message-ID: <CAAGC1OsCEgqhSNDCZaJ3tK_EEQwPHvqs+jsL3XRY3KeAhLRkGg@mail.gmail.com>
Subject: [PHP-DEV] Add $this return type
To: internals@lists.php.net
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From: radar3301@gmail.com (radar3301)

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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 = $name;

    return $this;
}

I propose to add "$this" as a return type, ie:

public function setName(?string $name): $this
{
    $this->name = $name;
    // implicit return $this;
}

public function setName(?string $name): $this
{
    $this->name = $name;
    // this would be an (compiler?) error
    return $somethingOtherThanThis;
}

public function setName(?string $name): $this
{
    $this->name = $name;
    $self = $this;
    // this would not be an error
    return $self;
}

public function setName(?string $name): $this
{
    $this->name = $name;
    // technically useless, but not an error
    return $this;
}

public function setName(?string $name): $this
{
    $this->name = $name;
    if ('foobar' === $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 an
alias for "static".

Regards,
radar3301

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<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 class=3D"gmail-Apple-interchange-newl=
ine">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 r=
eturn $self;</div><div>}</div><div><br>public function setName(?string $nam=
e): $this<br></div><div>{<br>=C2=A0 =C2=A0 $this-&gt;name =3D $name;</div><=
div>=C2=A0 =C2=A0 // technically useless, but not an error</div><div>=C2=A0=
 =C2=A0 return $this;</div><div>}</div><div><br>public function setName(?st=
ring $name): $this<br></div><div>{<br>=C2=A0 =C2=A0 $this-&gt;name =3D $nam=
e;</div><div>=C2=A0 =C2=A0 if (&#39;foobar&#39; =3D=3D=3D $name) {</div><di=
v>=C2=A0 =C2=A0 =C2=A0 =C2=A0 // not an error to return early</div><div>=C2=
=A0 =C2=A0 =C2=A0 =C2=A0 return;</div><div>=C2=A0 =C2=A0 }</div><div>=C2=A0=
 =C2=A0 // do some other stuff</div><div><br>=C2=A0 =C2=A0 // any of the ab=
ove legal examples</div><div>}</div><div><br></div><div>It should be obviou=
s, but functions outside of a class context would not be able to use this s=
yntax.</div><div><br></div><div>BC:</div><div>There would be no BC breaks, =
as this syntax is currently invalid (Parse error: syntax error, unexpected =
variable &quot;$this&quot;).</div><div><br></div><div>Other Considerations:=
</div><div>With regards to reflection and inheritance, &quot;$this&quot; wo=
uld be considered an alias for &quot;static&quot;.</div><div><br></div><div=
>Regards,</div><div>radar3301</div></div>

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