ADT / tagged union emulation?

[someniatko]

I'd like to mark somehow that my abstract class, or an interface, has only a restricted set of available extenders / implementers.

This can also be achieved on a language level by further extension of the enum concept as Larry Garfield planned. Also, another option is to use a union type, but it's too cumbersome to type each time.

[psalm-github-bot]

Hey @someniatko, can you reproduce the issue on https://psalm.dev ?

[AndrolGenhald]

Also, another option is to use a union type, but it's too cumbersome to type each time.

We have type aliases for that, though admittedly they could use some improvement.

I swear this has come up before, but I can't find anything right now.

[ZebulanStanphill]

DaveLiddament/php-language-extensions has an attribute called Sealed for this purpose. Sadly, there's no Psalm extension for this package yet (only a PHPStan one), but one for Psalm is planned.

[klimick]

See #1450

[someniatko]

Oh, thank you, that's a duplicate then!