use Test; role R[::T] { has T $.a } class A does R[subset :: of Int where {0 <= $_ <= 99}] {} class B does R[subset :: of Str where { .chars == 3 }] {} is A.new(:99a).a, 99; dies-ok { A.new: :999a }; is B.new(:a<bla>).a, "bla"; dies-ok { B.new(:a<aaaa>) }; done-testing