Test return constraints for role implementors (#3249)
Test return constraints for role implementors (#3249)

Closes https://github.com/rakudo/rakudo/issues/2385
MasterDuke17/rakudo,salortiz/rakudo,labster/rakudo,salortiz/rakudo,MasterDuke17/rakudo,MasterDuke17/rakudo,rakudo/rakudo,tbrowder/rakudo,salortiz/rakudo,rakudo/rakudo,tbrowder/rakudo,salortiz/rakudo,rakudo/rakudo,MasterDuke17/rakudo,tbrowder/rakudo,rakudo/rakudo,MasterDuke17/rakudo,labster/rakudo,salortiz/rakudo,labster/rakudo,tbrowder/rakudo,salortiz/rakudo,labster/rakudo,tbrowder/rakudo,tbrowder/rakudo,labster/rakudo,labster/rakudo,rakudo/rakudo,rakudo/rakudo,MasterDuke17/rakudo