match (self, update) {
            (this, Update::SetToSimple) => {*this = Test::Simple},
            (this, Update::SetToFoo) => {*this = Test::ComplexFoo(Foo::default())},
            (Test::ComplexFoo(ref mut c), Update::IncrementFoo(v)) => {c.0 += v},
            (Test::ComplexBar(ref mut c), Update::MultiplyBar(v)) => {c.0 *= v},
            _ => {}
        }