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Date: Sat, 9 Mar 2024 08:18:56 +0100
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Subject: [PHP-DEV] Idea: Implicit inheriting function argument & return type-hint
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From: marc@mabe.berlin (Marc)

Hi internals,

Based on the discussion of "Property accessor hooks, take 2​" and the 
set-hook argument type - I got to wonder why we still define "no type" 
as `mixed`.

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out-of-date, I have the feeling it would be better to force people to 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.

Example:

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
}
class C extends A {
     public function typed(mixed $var):mixed { return $var; } // 
explicit mixed to widen the type
}

That do you think?

This is just something that come to mind without having the knowledge 
nor time for this kind of RFC or implementation.

Greetings,
Marc