May be we should design something like ``` @JsVal...

# javascript

[konsoletyper]

May be we should design something like

@JsValueType
external sealed class Base() {
    class A(val x: Int) : Base()
    class B(val x: String) : Base()
}

with number of restrictions to external sealed classes marked with @JsValueType annotation. Say, without full RTTI (as we do with external interfaces) and with exactly one val parameter in primary constructors.