Data class toString name clash property / construction arg - kotlin

Question

Newby in Kotlin, I'm trying to implement a simple data class with constraint validation in fields.
This works great, but my solution is suboptimal since it exposes the private variables names defined in the class' definition in the toString representation, where I would prefer to have the properties:
data class MutablePointKt(private val _x: Int = 0, private val _y: Int = 0) {
private fun validatePositiveOrZero(some:Int) {
Validate.isTrue(some >= 0, "negative coordinate provided: $some")
}
var x: Int = 0
get() {
println(" > getting x: $field")
return field
}
set(value) {
validatePositiveOrZero(value)
field = value
}
var y: Int = 0
get() {
println(" > getting y: $field")
return field
}
set(value) {
validatePositiveOrZero(value)
field = value
}
init {
this.x = _x;
this.y = _y;
}
}
println(MutablePointKt(1, 2)) // prints "MutablePointKt(_x=1, _y=2)". how to print "MutablePointKt(x=1, y=2)" ?
Thank you !
EDIT:
I have a solution with
override fun toString(): String = ToStringBuilder.reflectionToString(this, KotlinToStringStyle()) and
class KotlinToStringStyle : ToStringStyle() {
private fun isFiltered(s: String?) = s?.startsWith("_") == true
override fun appendFieldStart(buffer: StringBuffer?, fieldName: String?) {
if (!isFiltered(fieldName))
super.appendFieldStart(buffer, fieldName)
}
override fun appendDetail(buffer: StringBuffer?, fieldName: String?, any: Any) {
if (!isFiltered(fieldName))
super.appendDetail(buffer, fieldName, any)
}
override fun appendFieldEnd(buffer: StringBuffer?, fieldName: String?) {
if (!isFiltered(fieldName))
super.appendFieldEnd(buffer, fieldName)
}
}
... but this is rather overkill, I would prefer a concise solution aka "the Kotlin way"