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Subject: Re: [PHP-DEV] Idea: Implicit inheriting function argument & return
 type-hint
Date: Sat, 9 Mar 2024 15:17:38 +0100
References: <5ac38d16-4b70-428e-ad80-87ae54839622@mabe.berlin>
To: php internals <internals@lists.php.net>
In-Reply-To: <5ac38d16-4b70-428e-ad80-87ae54839622@mabe.berlin>
Message-ID: <1773BB80-D9BD-4A0E-B01B-0A9EF402174D@cschneid.com>
From: cschneid@cschneid.com (Christian Schneider)

Am 09.03.2024 um 08:18 schrieb Marc <marc@mabe.berlin>:
> As the pseudo type `mixed` exists since PHP 8.0, which is already =
out-of-date, I have the feeling it would be better to force people to =
explicitly write `mixed` to widen the type of an overwritten function =
and let "no type" inherit the argument and return type of the parent.
>=20
> Example:
>=20
> class A {
>     public function typed(int $var): int { return $var; }
>     public function untyped($var) { return $var; } // implicit mixed =
as no overwrite
> }
> class B extends A {
>     public function typed($var) { return $var; } // implicit int as =
inherited from overwritten function
> }

This sounds like a bad idea to me as I cannot look at the function =
definition in class B and determine what the type of $var is.
On top of that: If the type of $var in A is changed then it would =
automatically also change in B. While this seems convenient it could =
also break B in subtle ways as the function suddenly gets different =
types than expected.

Regards,
- Chris