Bug #124392 for perl6: Roles can't use stub methods to indicate "must implement" methods: calls to such methods always ambiguous

Trying to tell doers of a role that they are expected to implement a method (a là Java interfaces) doesn’t seem to work. This role A { multi method a(Int $i) {...}; multi method a(Str $s) {...}; }; class B does A { multi method a(Int $i){0}; multi method a(Str $s) {"a"}; } ; B.new.a(0).say yields: Ambiguous call to 'a'; these signatures all match: :(B $: Int $i, *%_) :(B $: Int $i, *%_) in block <unit> at /tmp/0ILm1pfWyW:1 Both TimToady and timotimo suspect this to be a bug. See http://irclog.perlgeek.de/perl6/2015-04-22#i_10480886 for their discussion. Chris.