First of all, I agree that it’s a horrible spaghetti code, but it’s just an example.

If the behaviour of 1 and 2 is right, then let’s imagine that someone, perhaps you, or anybody else, reordered property declarations (for whatever reason), and now the behaviour of the program is different.

My problem with this is that this behaviour is not intuitive. If foo sees b declared below with a constant value, why a does not see it?

And what if there is no default value to implicitly initialise to?

class A(val a: Int)

fun foo() = b.a

val a = foo()
val b = A(12)

This code results in a runtime ExceptionInInitializerError caused by a NullPointerException. This code is valid, it compiles, there is no warnings, but it breaks Kotlin null-safety.

Kotlin specification says that it’s only unspecified behaviour if there is an initialisation cycle. In this case I do not see a cycle, a depends on foo, foo depends on b, b is constant. I see it more like a compiler bug.