The type of the variable used to reference an object and the type of the object being referenced.

There are always two possible types to consider. If you find you are having problems understanding casting then make sure that you keep in mind the following: In fact casting is slightly more subtle than this as it involves an object of a given type and a variable that references the object which can be of a different declared type. It would be very convenient for modeling state sets.Casting is the general practice of treating one object as if it was an object of another type.

There is another kind of usage I see for this feature. And I don't think they were a good idea in Scala to begin with. If you are not heavily into FP like the Kotlin guys (There is a remark by Andrey Breslav saying something similar to this: 'FP solves many problems easily, sometimes at a high price') implicits is not something you need. As I understand it they are mostly needed to create the blend of OOP and FP. My understanding of Scala is nevertheless not sufficient to say how problematic implicits really are. Several people replied and said this would seem a good idea to them and this really scared me. Unhappily, I didn't note down the link, but you should be able to google it. There was once a thread on Scala's user group where someone was asking for a special debugger to debug what implicit conversions are happening at runtime to better understand what is going on after compile time. Then they are a real problem for code readability if over used.

Scala's implicits are one of the major culprits for long compilation times. Even a conversion from Int to Long has to be done explicity. The Kotlin guys are very against implicits.

Kotlin any type