I have tried to explain the essential part of this in a comment to the related
issue. Regarding the traits, Elizabeth has mostly covered the subject. Coming
down to the `is hidden` trait, neither Any nor Mu are hidden:
say Any.^hidden; # 0
And, normally, no other class hides them:
say Int.^hides_parent(Any); # 0
Speaking about traits, `is hidden` makes a class hidden by setting
corresponding attribute on its metamodel object. Trait `hides` adds a parent to
the list of hidden parents on the child it is applied to. The second approach
is the way to have a class non-hidden by default but still exclude it from
method dispatch when necessary.
Best regards,
Vadim Belman
> On Aug 21, 2021, at 2:03 PM, Joseph Brenner <doom...@gmail.com> wrote:
>
> Given and example like this:
>
> class A {}
> class B is A {}
> class D is B {}
>
> say D.^parents(); # ((B) (A))
> say D.^parents( :all ); # ((B) (A) (Any) (Mu))
>
> So, I conclude that Any and Mu are "hidden" as far as ^parents is concerned.
>
> According to the documentation, ^mro_unhidden does this:
>
> "Returns a list of types in method resolution order, excluding
> those that are marked with is hidden."
>
> And yet, what I see is:
>
> say D.^mro_unhidden; # ((D) (B) (A) (Any) (Mu))
>
> So why does this include Any/Mu?
>
> A somewhat related question: How do you check whether a trait is set
> on something?
> Can you get a list of all traits?
>
> raku --version
> Welcome to 𝐑𝐚𝐤𝐮𝐝𝐨™ v2020.10.
> Implementing the 𝐑𝐚𝐤𝐮™ programming language v6.d.
> Built on MoarVM version 2020.10.
>
