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Any good examples of `FirTypeAttributeExtension`?

I'm trying to implement Scala's <https://docs.scala-lang.org/scala3/reference/experimental/cc.html|Capture Checking> as a FIR plugin. `FirTypeAttributeExtension` doesn't seem enough on its own though, and likely I have to add some checkers as well, no? Does `FirTypeAttributeExtension` affect call resolution as well? I don't actually want that, so I'm hoping it doesn't.

In fact it seems like what I'm asking for is some explanation of `ConeAttribute` and how to use it! Seems like it has `isSubtypeOf`, which is likely what I want!

The sandbox plugin has an example of `@Positive` and `@Negative` <https://github.com/JetBrains/kotlin/blob/b08685cd32b27f10ec449e9dce3c4c2bc0fcbbc5/plugins/plugin-sandbox/plugin-annotations/src/commonMain/kotlin/org/jetbrains/kotlin/plugin/sandbox/annotations.kt#L27-L31|annotations> which are <https://github.com/JetBrains/kotlin/blob/master/plugins/plugin-sandbox/src/org/jetbrains/kotlin/plugin/sandbox/fir/types/FirNumberSignAttributeExtension.kt|translated> to  an <https://github.com/JetBrains/kotlin/blob/b08685cd32b27f10ec449e9dce3c4c2bc0fcbbc5/plugins/plugin-sandbox/src/org/jetbrains/kotlin/plugin/sandbox/fir/types/FirNumberSignAttributeExtension.kt|attribute> which can then <https://github.com/JetBrains/kotlin/blob/b08685cd32b27f10ec449e9dce3c4c2bc0fcbbc5/plugins/plugin-sandbox/src/org/jetbrains/kotlin/plugin/sandbox/fir/checkers/SignedNumberCallChecker.kt|restrict function calls>. There's a <https://github.com/JetBrains/kotlin/blob/b08685cd32b27f10ec449e9dce3c4c2bc0fcbbc5/plugins/plugin-sandbox/testData/diagnostics/checkers/signedNumbersCheckers.kt|test> which shows some examples as well.

Given how underused as an extension it is, is it likely to go away? I know there's 0 guarantees about FIR extensions in general. I guess more so, are there any plans to get rid of it? Is it a maintenance burden? Or is it simple enough that like there's no reason to get rid of it short-term?
I know that's a difficult question to answer, so feel free not to! I'm just trying to figure out if I should build something purely using Checkers instead (since Checkers seem unlikely to go away in one form or another).

I think it's unlikely to go anywhere. ConeAttributes have significant use internally and this extension is a very low maintenance burden.