Submethods in roles

Hello,

I'm working on a fix for https://github.com/rakudo/rakudo/issues/2250. =
While the problem itself is easily tracks down to add_method not =
reporting a error, the general fix requires clear understanding of what =
happens to submethods when a role consumes another role. While things =
are pretty straightforward for methods, which are copied over from the =
source role to the target, for submethods not everything is so clear as =
I see it. Let's consider the following setup:

role R1 { submethod foo { "R1::foo" } }
role R2 does R1 { }
class Foo does R2 { submethod foo { "Foo::foo" } }

Imagine a code which would like to execute all submethods of all classes =
and roles. Normally, it would traverse mro and all role concretizations =
of each class from mro. In the example above such code would call =
submethod foo() from R1 twice: for R2 and R1 itself! Of course, there is =
a workaround for this as foo from R1 will have its .package set to R1. =
But what sense does such copying makes? When a role gets applied to =
class it does make some sense when we talk about BUILD/TWEAK/DESTROY. =
Though if https://github.com/rakudo/rakudo/issues/2241 gets implemented =
then even this use case will be obsoleted.

So, to have a comprehensive fix for #2250 I need to know how to handle =
submethods when a role is applied to a role: either I leave them =
untouched where they're (and this would be my choice); or I get them =
copied alongside with methods.

Best regards,
Vadim Belman
0
vrurg
2/6/2019 11:25:12 PM
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