Hi Kamil, the good news is that I understand what causes the problem. The bad news is that it I don't have a solution yet.
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The trouble is that you can't really call methods on roles; roles are rather abstract things, and if you try to call a method on a role, Perl 6 automatically creates a class for you, with the same name as the role. We call this process "punning". Calling R.^can($methodname) causes punning, and the punned class doesn't implement the stubbed method. Thus the error message. Knowing that, one could just inspect the role's method table instead of calling .^can. However that's not so easy, because roles come in groups. Roles can be parametric, and multiple roles of the same name can be parameterized by different signatures, and applying a role to a class (possibly with a list of arguments) selects a candidate role, not just a single role candidate. So far I haven't seen any method in the ParametricRoleGroupHOW that gives me a list of those candidates, or a of methods. So I don't know how to emulate .^can. I'll see if anybody in #perl6 (IRC) has a good idea... Cheers, Moritz On 19.05.2014 14:52, Kamil Kułaga wrote: > Hi Moritz, > > I've tried to adapt Your gist to something else but I've realized that > it does not work with stubs. Is it possible to bypass problem with > incomplete R? > > https://gist.github.com/teodozjan/b7183c81c966cfeee3bd > > I feel very inspired :) > > On Fri, May 16, 2014 at 10:44 AM, Moritz Lenz <mor...@faui2k3.org> wrote: >> Hi Kamil, >> >> >> On 05/15/2014 07:48 PM, Kamil Kułaga wrote: >>> >>> Is there any ordinary way (not something like getting list of methods >>> from base class) to ensure we are overriding method? >>> >>> Java has @Override annotation that that causes compilation error if >>> method is not necessary for Interface(Role). It is very handy if class >>> does many of them and someone cuts out deprecated method and there is >>> no reason to implement them any longer. >> >> >> Not by default, but the meta programming facilities make it just a small >> exercise to implement such a thing in user space. >> >> I've done that in >> https://gist.github.com/moritz/2c6ed01eef0029dabdeb >> >> Feel inspired :-) >> >> Cheers, >> Moritz > > >
