[perl #131676] doing a role fails to find inherited methods in some cases

[Brian S. Julin via RT]

On Mon, 07 Aug 2017 08:25:10 -0700, c...@zoffix.com wrote:
> On Thu, 29 Jun 2017 03:46:02 -0700, c...@zoffix.com wrote:
> > Mu provides iterator method, but when you mix in a role that wants it
> > implemented, it doesn't find it:
> >
> > m: role Meow { method iterator {…} }; class Bar does Meow {}
> > camelia     rakudo-moar 2a8d1e: OUTPUT: «5===SORRY!5=== Error while
> > compiling <tmp>␤Method 'iterator' must be implemented by Bar
> > because
> > it is required by roles: Meow.␤at <tmp>:1␤»
> >
> > Yet it all works fine if you are also doing `is SomethingUnrelated`:
> >
> > m: class Foo { method x {} }; role Meow { method iterator {…} };
> > class
> > Bar is Foo does Meow {}
> > camelia     rakudo-moar 2a8d1e: ( no output )
> 
> 
> Another example turned up; fails to notice the method is provided by
> `handles`:
> 
> class HTTP::Header does Associative does Iterable {
>     subset StrOrArrayOfStr where Str | ( Array & {.all ~~ Str} );
> 
> has %!fields of StrOrArrayOfStr
>              handles <AT-KEY EXISTS-KEY DELETE-KEY push
>                       iterator list kv keys values>;
> 
> method Str { #`[not shown, for brevity] }
> }
> 
> This is from https://github.com/perl6/doc/issues/1438


Rakudo PR request 1170 submitted to address this.

With that patch applied both above examples work and this still fails, as it 
should:

$ perl6 -e 'class Foo { method x {} }; role Meow { method elems {…} }; class 
Bar is Mu does Meow {}'
===SORRY!=== Error while compiling -e
Method 'elems' must be implemented by Bar because it is required by roles: Meow.
at -e:1