Is this a known gotcha?: https://try.kotlinlang.org/#/UserProjects/gtd3usu4s8thgaq0dllbptk1ho/199jpkdpd1at7m7rve3v1hrl4v

Yup, Similar to

abstract class A(val a: A?)

object B: A(C)
object C: A(B)
...
println("${B.a} and ${C.a}")

I wouldn't hate the editor and/or compiler generate a warning in this case

It may slow the compiler down too much if it has to analyze the code for this type of situation. In the above example, the circular definition is trivial and simple, but you can make a circular definition very deep and non-trivial.