[RFC] [Under Discussion] Sealed Classes

Hello internals,

Following up on last years email, I have decided to move along with the

Sealed classes RFC after some changes, and put it up for discussion.

Previous discussion: https://externals.io/message/114116

RFC: https://wiki.php.net/rfc/sealed_classes

Why not "final ... permits" or "final ... for" as options? Effectively what is created here is a final class/classic-thing, but with holes in it. Otherwise, there become questions about why final and sealed have different keywords when they're such similar things.

--Larry Garfield

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I personally see sealed and final as completely different flags.

one ( final ) declares a type as final, therefore, no sub-type can exist at runtime.

while the other ( sealed ) declares a type as non-final, with known, limited set of sub-types.

another things to note, is that final modifier is currently not supported on traits, and interfaces, and while we could add this, it still feels "wrong" when you see final interface FooInterface .. at first glance, making it harder to read the code.

However, i see why people might prefer this option, so if enough people request this, i will add it as a syntax option.

Cheers,

Saif.