[Codegen] Compilation error when DataObject includes MutableList

[rgmz]

Given the following (contrived) data object:

@DataObject(generateConverter = true)
class StudentList() {
    var names: MutableList<String> = mutableListOf()

    constructor(json: JsonObject) : this() {
        StudentListConverter.fromJson(json, this)
    }

    fun toJson(): JsonObject = JsonObject.mapFrom(this)
}

The generated helper functions will incorrectly use toList() (IMMUTABLE) instead toMutableList():

fun studentListOf(names: Iterable<String>? = null): StudentList = io.vertx.example.StudentList().apply {
  if (names != null) {
    this.names = names.toList()
  }
}

Which results in a compilation error (inferred type is List<String> but MutableList<String> was expected):

> Task :compileKotlin FAILED

e: ~/foo/build/generated/source/kaptKotlin/main/io/vertx/example/StudentList.kt: (34, 22): Type inference failed. Expected type mismatch: inferred type is List<String> but MutableList<String> was expected

[rgmz]

Based on my initial research, it does not appear possible to differentiate List and MutableList. :disappointed:

...Compile-time references to List and MutableList are both compiled to java.util.List references. Therefore, it's not possible to detect whether a list is a MutableList at runtime.

Edit: you can seemingly cast toList() as toList() as MutableList<String>, although I'm not certain the impact of this.