The position class of a chess game in kotlin

Position.kt

internal data class Position(val name: String) {

    constructor(file: Int, rank: Int) : this("${(file + 'A'.toInt()).toChar()}${rank + 1}")

    val file: Int = name.validateAndTransform { it[0] - 'A' }
    val rank: Int = name.validateAndTransform { it[1].toString().toInt() - 1 }

    private fun <T> String.validateAndTransform(trasformer: (String) -> T): T =
        if (Regex("""^[A-H][1-8]$""") matches this)
            trasformer(this)
        else
            throw IllegalStateException("position name must be of one letter from A to H and one number from 1 to 8")

    /**
     * @return the name of this position
     */
    override fun toString() = name
}