This would prevent extra branching in 'as <not-null-type>', which usually would not be covered.
We can't rely on argument type nullability here, because it still can hold an uninitialized value on JVM. KT-50577 KT-35272 KT-27427
#KT-6007 #KT-16445 #KT-17753 #KT-22488 #KT-23881 #KT-24135 #KT-26360 #KT-27427 #KT-27449 #KT-27830 #KT-28042 #KT-29595 #KT-30708 #KT-32793