Error:(39, 17) Kotlin: Type inference failed: fun ...

# tornadofx

[pike]

Error:(39, 17) Kotlin: Type inference failed: fun <S> TableView<S>.nestedColumn(title: String, op: (TableView<S>.(TableColumn<S, Any?>) -> Unit)? = ...): TableColumn<S, Any?>
cannot be applied to
receiver: TableView<Usage!> arguments: (String,TableView<Usage!>.(TableColumn<Usage!, Any?>) -> TableColumn<Usage, Int>)