Null references redux

[bearophile]

downs:

> Basically, anything that may fill it with nulls.
> 
> The only two allowed instructions would be ~= NonNullable and ~= NonNullableArray. And it's good that way.

I agree.
In such situation I'd also like to have a default method to insert one or more nonnull items in any point of the array (see insert method of Python lists, that can also be expressed as s[i:i]=[x]). Having fee basic default methods will help keep such safe arrays flexible.

Bye,
bearophile