What Kotlin feature is used for

object Users : Table() {
    val id = varchar("id", 10).primaryKey() // Column<String>
    val name = varchar("name", length = 50) // Column<String>
    val cityId = (integer("city_id") references Cities.id).nullable() // Column<Int?>
}
Users.insert {
            it[id] = "andrey"
            it[name] = "Andrey"
            it[cityId] = saintPetersburgId
        }

how compiler know that

it[id]

is valid and for example

it[title]

is not valid?

It's due to a closure that passed into

insert

is defined like:

body: T.(InsertStatement<Number>) -> Unit

where

T: Table

Thus all properties of the

Users

table are available inside the closure.