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Date: Fri, 17 May 2024 10:34:42 +0200
To: internals@lists.php.net
Subject: Re: [PHP-DEV] [RFC] [Vote] Type Guards for Classes
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From: langemeijer@php.net ("Casper Langemeijer")

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On Thu, May 16, 2024, at 22:31, Patrik V=C3=A1clavek wrote:
> This feature aims to simplify and standardize the process of verifying=
 that a variable is an instance of a specific class, enhancing code read=
ability and reducing boilerplate code.
>=20
> Currently, in PHP, to ensure that a variable is an instance of a speci=
fic class, developers need to use the `instanceof` operator and manually=
 throw an exception if the check fails. This results in repetitive boile=
rplate code scattered throughout the codebase. A new syntax, `(ClassName=
) $variable`, is proposed to streamline this process by performing an in=
stanceof check and throwing a `TypeError` if the variable is not an inst=
ance of the specified class.

I view variables changing types to be an anti-pattern.

Instead if adding type guards, I would rather see this problem solved by=
 having typed local variables. This ensures that a variable always holds=
 a specific type, avoiding the need of repetitive scattered type guards.=
 Working with variables would then be the same as working with class pro=
perties. They could be typed or untyped.

Also, I see the need for type guards as a symptom of bad composition. Mo=
stly methods that are too large would benefit. If a method is decomposed=
 into smaller methods the use of parameter and return type checks it's u=
nlikely there is need for additional type guards.
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<!DOCTYPE html><html><head><title></title><style type=3D"text/css">p.Mso=
Normal,p.MsoNoSpacing{margin:0}
p.MsoNormal,p.MsoNoSpacing{margin:0}</style></head><body><div>On Thu, Ma=
y 16, 2024, at 22:31, Patrik V=C3=A1clavek wrote:<br></div><blockquote t=
ype=3D"cite" id=3D"qt" style=3D""><div>This feature aims to simplify and=
 standardize the process of verifying that a variable is an instance of =
a specific class, enhancing code readability and reducing boilerplate co=
de.<br></div><div><br></div><div>Currently, in PHP, to ensure that a var=
iable is an instance of a specific class, developers need to use the `in=
stanceof` operator and manually throw an exception if the check fails. T=
his results in repetitive boilerplate code scattered throughout the code=
base. A new syntax, `(ClassName) $variable`, is proposed to streamline t=
his process by performing an instanceof check and throwing a `TypeError`=
 if the variable is not an instance of the specified class.<br></div></b=
lockquote><div><br></div><div>I view variables changing types to be an a=
nti-pattern.<br></div><div><br></div><div>Instead if adding type guards,=
 I would rather see this problem solved by having typed local variables.=
 This ensures that a variable always holds a specific type, avoiding the=
 need of repetitive scattered type guards. Working with variables would =
then be the same as working with class properties. They could be typed o=
r untyped.<br></div><div><br></div><div>Also, I see the need for type gu=
ards as a&nbsp;symptom of bad composition. Mostly methods that are too l=
arge would benefit. If a method is decomposed into smaller methods the u=
se of parameter and return type checks it's unlikely there is need for a=
dditional type guards.<br></div></body></html>
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