Possible D2 solution to the upcasting array problem, and a related problem with const and nested arrays

[Stewart Gordon]

<snip>
> - given invariant(int)[][], both possible conversions are covered
> -- const(int[])[] by first applying 1(b) to invariant(int) and then by 
> applying 2(a) with T = const(int)[]
> -- const(invariant(int)[])[] by just applying 1(b) to invariant(int)[]
<snip>

Hang on ... this involves applying 2(a) as well.

Stewart.