Result of the `checkNotNull` calls should always be a non-nullable
values.
The simplest idea how to acheive it is adding not-nullable Any bound
to the type parameter declaration.
Existing comment stating about impossibility of such bound seems to be
not 100% correct because it doesn't take into account presence of
definitely-non-nullable X & Any types that allow described case with
nullable generic.
^KT-55804 Fixed
Denis.Zharkov