On Fri, Aug 16, 2024, at 16:17, Larry Garfield wrote:
> On Fri, Aug 16, 2024, at 6:35 AM, Alexandru Pătrănescu wrote:
> > Hi Nick,
> >>
> >> Is there any interest in having enums as class constants?
> >>
> >> I'm often finding cases where I would like to have an enum inside of a
> >> class, but don't want a free-floating enum that's basically like
> >> another class.
> >>
> >
> > ...<snip>...
> >
> >>
> >> class SSHClient {
> >>
> >> public const enum CommandResult
> >> {
> >> case Success;
> >> case Failure;
> >> case Unknown;
> >> case Timeout;
> >> }
> >>
> >> // ...
> >> }
> >>
> >>
> >> // Usage:
> >>
> >> SSHClient::CommandResult::Success
> >
> >
> > I feel this topic could be maybe more broad and be called "nested
> > classes" that are already supported in multiple languages: Java, Swift,
> > Python, C#, C++, JavaScript, etc.
> >
> > The syntax you showed is usually identical with what other languages
> > use, except that probably the const is unnecessary.
> > The nested class can have visibility as sometimes having it private
> > makes sense.
> > Accessing it through `::` is probably fine, but a deeper look at the
> > grammar might be necessary.
> > The nested class would have access to parent class private properties
> > and methods.
> >
> > I also mentioned this topic on the subject of defining a type in an
> > autoloader compatible way.
> > And indeed, a type could also be defined nested in a class if we want
> > to support that as well.
> >
> > Now, this feature is not simple, and I think it needs proper
> > sponsorship from someone experienced with internals.
> >
> > Regards,
> > Alex
>
> I agree with Alexandru. Since enums are 90% syntactic sugar over classes,
> "inner enums" would be 80% of the way to "inner classes". And I would be in
> favor of inner classes. :-) There's a lot of potential benefits there, but
> also a lot of edge cases to sort out regarding visibility, what is allowed to
> extend from what, etc. But that would support inner enums as well.
>From recently looking into this for totally unrelated reasons, nested enums
>would be far easier to implement on a grammar level. Enums also have some
>constraints that make it simpler than the general “nested classes,” such as
>rules regarding inheritance.
As for the actual implementation, it’ll be the edges that kill you.
I would recommend just doing enums, and keep the scope smaller.
