cast<
Provides a view of this iterable as an iterable of R instances.
If this iterable only contains instances of R, all operations
will work correctly. If any operation tries to access an element
that is not an instance of R, the access will throw instead.
When the returned iterable creates a new object that depends on
the type R, e.g., from toList, it will have exactly the type R.
Implementation
Set<T> cast<T>() {
if (this is MapKeySet<T>) {
return this as MapKeySet<T>;
}
return Set.castFrom<E, T>(this);
}