kotlin-reflect

// this should be generated by walking of the child classes of visitable
interface Visitor {
    visitExpression(expression: Expression)
    visitStatement(statement: Statement)
}

abstract class Visitable {
    fun accept(visitor: Visitor) {
        // name of the visit function
        val thisKClass = this.javaClass.kotlin
        val name = thisKClass.simpleName
        val functionName = "visit$name"

        // find the function on the visitor
        val vKClass = visitor.javaClass.kotlin
        val functions = vKClass.memberFunctions
        val function = functions.find { it.name == functionName } ?: throw RuntimeError("Could not find visit function called '$functionName' on visitor", null)
        function.call(visitor, this)
    }
}

class Expression : Visitable()
class Statement : Visitable()


// Another option would be:

// this should be generated by walking of the child classes of visitable
interface Visitor {
    visitExpression(expression: Expression)
    visitStatement(statement: Statement)
}

interface Visitable {
    fun accept(visitor: Visitor)
}

class Expression : Visitable() {
    fun accept(visitor: Visitor) {
        visitor.visitExpression(this)
    }
}
class Statement : Visitable() {
    fun accept(visitor: Visitor) {
        visitor.visitStatement(this)
    }
}

// But where is the fun in that :)