[perl #128211] multi BUILD defined in role gets messed up in sub-class

[via RT]

# New Ticket Created by  Jonathan Stowe 
# Please include the string:  [perl #128211]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=128211 >


Consider the following:

role Foo {
    has $!attribute;
    multi submethod BUILD(Str :$!attribute!) {
        say "with attribute";
    }
}

class Bar does Foo {
    multi submethod BUILD(Str :$foo!) {
        say "with foo";
        $!attribute = "default";
    }

    method foo() {
        say $!attribute;
    }
}

class Zub  is Bar {
}

Bar.new(attribute => "set").foo;
Bar.new(foo => "something").foo;

Zub.new(attribute => "set").foo;
Zub.new(foo => "something").foo;


Resulting in:

with attribute
set
with foo
default
Cannot call BUILD(Zub: Str); none of these signatures match:
    (Bar $: Str :$foo!, *%_)
    (Bar $: Str :attribute($!attribute)!, *%_)
  in block <unit> at tt line 25


It appears that it is trying to call the BUILD with a *positional* in the 
sub-class, however supplying the candidate that it reports it is trying to call 
doesn't effect the outcome, which is somewhat odd in itself.  

Unfortunately the call path which leads to this state of affairs is not clear 
to me at all.