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kotlinlang

I have a unary `annotation class` that accepts a `KClass&lt;*&gt;`. If I want to retrieve the type in my compiler plugin,
```@OptIn(SymbolInternals::class) annotatedClass.fir.annotations
    .first { annot -&gt;
        annot.annotationTypeRef.coneType.classId == ANNOTATION_CLASS
    }
    .argumentMapping
    .mapping
    .values
    .single()
    .resolvedType
    .classId!!,```
Is this the best I can do?

What’s the difference between the current `first` predicate
```annot.annotationTypeRef.coneType.classId == ANNOTATION_CLASS```
and this alternative?
```@OptIn(UnresolvedExpressionTypeAccess::class)
annot.coneTypeOrNull?.classId == ANNOTATION_CLASS```

I believe there's a `FirAnnotation.getXArgument` family of extensions that can help you here. `getKClassArgument` should be the one you're looking for <https://github.com/JetBrains/kotlin/blob/master/compiler%2Ffir%2Fproviders%2Fsrc%2Forg%2Fjetbrains%2Fkotlin%2Ffir%2Fdeclarations%2FFirAnnotationUtils.kt#L214|(source)>

<@U019AG342E5> Wow, `.getKClassArgument(Name.identifier("kClass"))` should do the job then, right? (Is there a better way to obtain the `Name`, eg by querying the annotation class?) This is so much better, thank you!

Also, I’ve browsed the API a little bit,
```@OptIn(SymbolInternals::class) annotatedClass.fir.annotations
    .getAnnotationByClassId(classId = ANNOTATION_CLASS, session = this.session)```
And I think this is better than
```@OptIn(SymbolInternals::class) annotatedClass.fir.annotations
    .first { annot ->
        annot.annotationTypeRef.coneType.classId == ANNOTATION_CLASS
    }```
This current version. But are there any subtle differences I should be aware of? Or can it be improved even further?

```annotatedClass
    .getAnnotationByClassId(classId = ANNOTATION_CLASS, session = this.session)!!```


`getAnnotationByClassId` seems to be better AFAIK. In general, I prefer using these utilities than accessing `argumentMapping` and such directly 
Re: querying the name: I think you can use `session.symbolProvider.getClassLikeSymbolByClassId` <https://github.com/JetBrains/kotlin/blob/master/compiler%2Ffir%2Fproviders%2Fsrc%2Forg%2Fjetbrains%2Fkotlin%2Ffir%2Fresolve%2Fproviders%2FFirSymbolProvider.kt#L40|(source)> to get the annotation class. What I've seen people do instead is add the relevant annotations library as a dependency in their plugins, and thus get access to the names from there (e.g. by doing `MyAnnotation::kClass.name`)

<@U019AG342E5> Yes, I’ll use `getAnnotationByClassId`. Thanks for helping me discover it! Also, you mean by doing `Name.identifier(MyAnnotation::kClass.name)`, right? I also like this, thank you!