[perl #122497] "This type cannot unbox to a native string" error on jvm, parrot

[Christian Bartolomaeus via RT]

This works now (again):

$ perl6-j -e 'BEGIN my %cache = 1 => 0; sub foo($n) {%cache{$n}:exists}; say 
foo(42)'
False
$ perl6-p -e 'BEGIN my %cache = 1 => 0; sub foo($n) {%cache{$n}:exists}; say 
foo(42)'
False
$ perl6-m -e 'BEGIN my %cache = 1 => 0; sub foo($n) {%cache{$n}:exists}; say 
foo(42)'
False

I unfudged the skipped tests and added a new test for the above code to 
S32-hash/exists-adverb.t with commit 
https://github.com/perl6/roast/commit/317910afbd

I'm closing this ticket now.