Lexical scope of parametric declaration blocks

[Ashley Winters]

In S12, I see examples like:

role Pet[Type $petfood = TableScraps] {
        method feed (::($petfood) $food) {...}
}

I assume that means lexicals declared as part of a parametric
specialization declaration block thingy are only visible within that
scope, like a formal subroutine parameter list?

If so, are there things allowed (or disallowed) in type parameter
lists vs. sub parameter lists?

If [] is enforcing long-name generation or something simple like that,
could I cheat and make it imply multi on my functions if I use it?

sub foo[Int $x: Pair ?$y] {...} 
sub foo[Pair $x, Pair $y] {...}

Would that be valid/mean anything?

Okay, that enough curiosity for today. :)

Thanks,
Ashley Winters