What is `versionRequirements` in the kotlin metada...

# compiler

[mbonnin]

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.

[ephemient]

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

[mbonnin]

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

[udalov]

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

[mbonnin]

Thanks!