Exposing a Mutable member as Immutable

Language Design
23

Is it to late for Kotlin to add an equivalent of C++ const keyword ?

class MyClass {
    const fun bar() { ...} // 'const' mean bar doesn't change state of this 
    fun baz() { ... } // 
}

class Demo {
     private val _theThing = MyClass()
         get theThing: const MyClass
}

fun main() {
    Demo().theThing.bar() // legal
    Demo().theThing.baz() // not legal => getter implie const object, baz function not declared const
}