her_not_void: other /= Void
        external
            "built_in"
        ensure
            shallow_implies_deep: standard_is_equal (other) implies Result
            same_type: Result implies same_type (other)
            symmetric: Result implies other.is_deep_equal (Current)
        end

    frozen deep_equal (a: detachable ANY; b: like a): BOOLEAN
            -- Are `a' and `b' either both void
            -- or attached to isomorphic object structures?
        do
            if a = Void