Ok, I found the issue. There is something wrong with org.jetbrains.dokkadokka analysis1.8.20. Because it embedded a

org.jetbrains.kotlin:kotlin-compiler:1.8.10

via shadow jar. That is the reason why it is working perfectly on Gradle 8.1.1. https://repo1.maven.org/maven2/org/jetbrains/dokka/kotlin-analysis-compiler/1.8.20/kotlin-analysis-compiler-1.8.20.jar (51.8 MB) OMFG.

Hm, maybe it indeed is Dokka in your case. Somehow it seems to now use the Kotlin Gradle Plugin 1.8.20 with the embeddable Kotlin Compiler 1.8.10 in my project, though I don't think I changed anything. The KGP then has the

DefaultLanguageSettingsBuilderKt

class that references

KOTLIN_2_0

from a class in the Kotlin compiler which is not yet found in 1.8.10. 😕

But I didn't touch that in the last 3 months or so. 😕

And on GitHub Actions, the same build still runs perfectly fine. So at least in my case it has to be something local

Oh, I'm blind, shout-out to build scans. I locally added an

implementation(enforcedPlatform(kotlin("bom")))

. Without that, the

implementation(embeddedKotlin("compiler-embeddable"))

is upgraded to 1.8.20, now it is nailed to 1.8.10 which then breaks it. 🙈

I have a new idea of this. I think we could get rid of Gradle's Kotlin version by moving the generation code out of the

initialization

module that my Elucidator shows above. Use a GradleRunner to run a JVM application module.

I will confirm the feasibility of this method when I am free. I'll let you guys know the result here after I try it.

Yeah, I have confirmed that the above method can work really well!