[perl #122220] "@list is copy" leads to dependent default parameters not updating

[Christian Bartolomaeus via RT]

This works now as expected (on 'nom' and 'glr'):

$ perl6-m -e 'sub a(@list is copy, $l = @list.elems) { say "Elems: " ~ 
@list.elems; say "l: $l"; }; a(<a b c d e f g>); a(<a b c>)'
Elems: 7
l: 7
Elems: 3
l: 3

I added a test to S06-traits/is-copy.t with commit 
https://github.com/perl6/roast/commit/4747cd49fc

I'm closing this ticket as 'resolved'.