Just found ticket https://rt.perl.org/Ticket/Display.html?id=123396 which reasons about 'role A::B {}; sub foo(A $a) {}' and the like.
I'll add the bit about 'role A::B { method foo(A $a) { } }' to that ticket,
since it seems to be a separate problem.
If noone objects, I'm going to close this ticket.
