Dominance in pattern matching for switch: Spec and Javac inconsistency

[John Rose]

On Sep 3, 2021, at 7:00 AM, forax at univ-mlv.fr wrote:
> 
> 
> but a guarded switch dominates it's prefix,
> e.eg
>   case Integer i && foo(i) dominates case Integer.
> 
> But there is no rule between a guarded pattern like case Integer i && foo(i) and case 1, so they can appear in any order.
> 

Surely that’s a simple oversight.

FWIW, it would be possible to convert reasoning about value-set
inclusion to reasoning about type dominance, in this case, by
simulating T x && g(x) as an existential type (? extends T).

I think that simulation has the right properties for guards,
which is that (a) no two guards denote the same static value
set and (b) any guarded value set is a subset (possibly improper)
of the corresponding unguarded value set.