I had a weird bug today regarding

when

. I have a field that holds an enum value and in another place, I have an (exhaustive) when given that field. So the parameter of the

when

was of type

T

. Then, I changed the field to be instead a

LiveData<T>

. A lot of places in my source threw errors and I fixed them by calling

.value

on the field. But the

when

did not threw an error (as the when does not return anything, the fact that is is no longer exhausive is not an error). But why can I even write:

when(status /* type = LiveData<T>*/) {
   T.FIRST_VALUE -> { ... }
   T.SECOND_VALUE -> { ... } 
   T.THIRD_VALUE -> { ... }

as status can never be any of these types? When I try the same structure with a String as parameter, it throws an error (incompatible types).

I don't know the answer, but I can provide some logic. LiveData is abstract, its equals function probably is open, so the compiler cant make assumptions at compile time.

I tried it with a class that is not open (my own subclass of LiveData) and it still worked like LiveData

Then the compiler is probably dealing with special cases