I created a YouTrack issue for a proposal for mandatory varargs (varargs which have a minimum size of 1) here:
https://youtrack.jetbrains.com/issue/KT-55890/Mandatory-varargs
The proposed syntax would be similar to:
fun nonEmptyListOf(mandatory vararg value: String): NonEmptyList<String> = …
Please give your opinion and vote on the issue 🙂