How do I get the KClass of a constructor parameter in kotlin?

I want to create some sort of dependency injection system taking a list of classes that need to be instantiated to create a sort of dependency tree. For that I want to take all the classes and first of all find their "external dependencies" (the classes that are not contained in the tree).

My problem is: In kotlin, the parameters of a constructor (KFunction) are saved as types of which I don't know how to get the classes which I really need.

So the question is: How can I get the actual KClasses of constructor parameters in kotlin?