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kotlinlang

Is there a comparison resource somewhere of how the JDK impacts generated Kotlin code? I'm particularly interested in changes since Java 11. Does targetting a more recent Java version change the generated code, and how?

At the moment, I think there are only two features which are affected by JVM bytecode target version:
1. If JVM target &gt;= 9, string concatenation uses invokedynamic
2. If JVM target &gt;= 17, the `PermittedSubclasses` attribute is written, which makes switches over Kotlin sealed classes exhaustive in Java
But there are plans to support more, e.g. <https://youtrack.jetbrains.com/issue/KT-65688|KT-65688>.

Did a quick search for `&gt;= JvmTarget` and those were the 2 results indeed: <https://github.com/search?q=repo%3AJetBrains%2Fkotlin%20%20%3E%3D%20JvmTarget&amp;type=code>

Maybe Records? <https://github.com/JetBrains/kotlin/blob/df027063420af0abd48c64ef598b1c5b0b5d7b1b/compiler/frontend.java/src/org/jetbrains/kotlin/resolve/jvm/checkers/JvmRecordApplicabilityChecker.kt#L165|https://github.com/JetBrains/kotlin/blob/df027063420af0abd48c64ef598b1c5b0b5d7b1b/[…]ns/kotlin/resolve/jvm/checkers/JvmRecordApplicabilityChecker.kt>

Yeah, records (`@JvmRecord data class`) are kinda related, but not really, since they are just forbidden unless JVM target is at least 15.

Yea the user needs to opt-in but still an incentive to bump `jvmTarget`