interface I0
    method foo
        0
end

interface I1
    method bar
        1
end

interface I
    is I0
    is I1
    method quux
        2
end

class C {}
    is I
end

class Main {}
    class method foo: x::I0
        x::I::C foo
    class method bar: x::I1
        x::I::C bar
    class method quux: x::I
        x quux
    class method run: cmd in: sys
        let c = C new.
        sys output println: "foo: {self foo: c} => I0 ok".
        sys output println: "bar: {self bar: c} => I1 ok".
        sys output println: "quux: {self quux: c} => I ok"
end