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

[via RT]

# New Ticket Created by  Zoffix Znet 
# Please include the string:  [perl #131676]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=131676 >


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 )