castFrom<S, T> method
override
Adapts source to be a List<T>.
Any time the list would produce an element that is not a T,
the element access will throw.
Any time a T value is attempted stored into the adapted list,
the store will throw unless the value is also an instance of S.
If all accessed elements of source are actually instances of T,
and if all elements stored into the returned list are actually instance
of S,
then the returned list can be used as a List<T>.
Implementation
static List<T> castFrom<S, T>(List<S> source) => CastList<S, T>(source);