[perl #127303] multi required by role doesn't work with .^mixin

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# New Ticket Created by  Lloyd Fournier 
# Please include the string:  [perl #127303]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=127303 >


role multirequire {
    multi method runtime($var) {...}
}

class Foo  {
    multi method runtime($var) { }
}

Foo.^mixin(multirequire);

Multi method 'runtime' with signature :(Foo+{multirequire} $: $var, *%_)
must be implemented by Foo+{multirequire} because it is required by a role

change that to a does and it works fine.