multi BUILD annoying

gistfile1.txt

role Foo {
	has $!attribute;
	multi submethod BUILD(:$!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 does Foo {
}

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

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