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Subject: Re: [PHP-DEV] [RFC] Interface Default Methods
From: rowan.collins@gmail.com (Rowan Tommins)

On 19/06/2023 20:20, David Gebler wrote:
> Okay, thanks. That's really quite significant, since it changes the feature
> to one which could allow changes made to interfaces to adversely impact
> existing clients of an interface without those clients changing a thing.


As the RFC says, it introduces a form of multiple inheritance, and 
inheritance in PHP doesn't make any such guarantee - to adapt your example:

class A {
     public function foo(): void {
         $this->bar();
     }
}

class B extends A {
     public function bar(): void {
         ...
     }
}

The job of detecting that class A doesn't define a contract for method 
bar falls to static analysers, and the same would be true for default 
implementations on interfaces.


Regards,

-- 
Rowan Tommins
[IMSoP]