What is

versionRequirements

in the kotlin metadata? Is it a build-time requirement? stdlib requirement? something else? Adding

-Xjvm-default=all

adds a Kotlin 1.4 requirement on the generated class and I'm curious the reason.

https://youtrack.jetbrains.com/issue/KT-4779 was added in Kotlin 1.4 so that seems to make sense

Right. Thanks! Never realized there was per-class version requirements. I though it was all based on the top level metadata version.

There’s some info in the

KmVersionRequirement

class from kotlinx-metadata-jvm: https://github.com/JetBrains/kotlin/blob/7620289f6f7151257acd3178a9f64cf4401adf07/libraries/kotlinx-metadata/src/kotlinx/metadata/Nodes.kt#L973 Also see kdoc on the related internal class `RequireKotlin`: https://github.com/JetBrains/kotlin/blob/7620289f6f7151257acd3178a9f64cf4401adf07/libraries/stdlib/src/kotlin/internal/Annotations.kt#L89

Thanks!