Caveats of Kotlin Delegation

Implementation caveat

In the example we’ve created so far, the Manager may delegate calls to an instance of a JavaProgrammer, but a reference to a Manager may not be assigned to a reference of a JavaProgrammer—that is, a Manager may use a JavaProgrammer, but a Manager may not be used as a JavaProgrammer. In other words, a Manager has a JavaProgrammer but is not a kind of JavaProgrammer. Thus, delegation offers reuse without accidentally leading to substitutability as inheritance does.

However, there’s one small consequence of how Kotlin implements ...