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Subject: Re: [PHP-DEV] enum flag backed enum
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From: weedpacket@varteg.nz (Morgan)

On 2025-09-04 09:23, Marc B. wrote:
>>
>> Attempting to use a backed value that is not a power-of-two would result in a compilation error. Bitwise operations are performed as though they’re performed on a regular integer.
>>
>> What do you think?
> 
> I think what we actually would need is an EnumSet which can be used with any enum but (based on its ordinal) but this would play nicely together with generics `new EnumSet<JsonOption>`.
> 

Agreed; using enums-backed-by-powers-of-two is just a way to encode sets 
of values drawn from an enum (it's a way to enumerate the possible 
subsets of a set). It should be possible to have a set of Enum values 
for any Enum, rather than break the Enum type concept by exposing 
implementation details, and allow sets for some types but not others 
depending on how they are serialised.

A class can be built in userspace as a "SetOfEnum"; or such a class 
could be added to the standard library; or even have, for each Enum 
declared, an EnumSet (final) class is also implicitly declared.