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Subject: Re: [PHP-DEV] [IDEA] allow extending enum
From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=c3=bcsterhus?=)

Hi

On 3/29/23 11:42, Sebastian Bergmann wrote:
> Am 29.03.2023 um 11:31 schrieb Rokas Šleinius:
>> I wouldn't say removing the final attribute from enums actually "breaks" any functionality.
> 
> I am with Marco on this: removing the "finality" from enum would be a
> major backward compatiblity break as it breaks a fundamental assumption
> about enums.
> 

And to give a specific example from PHP 8.3: As part of the Randomizer 
additions RFC (https://wiki.php.net/rfc/randomizer_additions), PHP 8.3 
got its first "natively included" enum (\Random\IntervalBoundary). This 
enum works together with the new Randomizer::getFloat() method to 
specify if the given min and max value may be returned or not.

The Randomizer::getFloat() method internally includes switch statement 
that chooses the implementation based on the IntervalBoundary value given.

If a user would be able to extend the IntervalBoundary enum, the method 
would not be able to make sense of it.

The IntervalBoundary enum completely enumerates all four possible 
combinations for the two possible states for each of the two boundaries 
(2*2 = 4). By definition there is no other valid value.

Best regards
Tim Düsterhus