Macro dyn_context::impl_stop_and_drop

macro_rules! impl_stop_and_drop {
    (
        $($token:tt)+
    ) => { ... };
}

Helps to not forget to implement Drop when implementing Stop.

Accepts input in any of following forms:

for $t:ty {
    $($impl_stop_trait_body:tt)*
}

<$generics> for $t:ty $(where $where_clause)? {
    $($impl_stop_trait_body:tt)*
}

Example:

struct Component {
    is_running: bool,
}

impl Default for Component {
    fn default() -> Self {
        Component { is_running: false }
    }
}

#[derive(Default)]
struct MyState {
    components: [Component; 32]
}

impl SelfState for MyState { }

#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
struct ComponentId(u8);

impl ComponentId {
    fn run(self, state: &mut dyn State) {
        let my_state: &mut MyState = state.get_mut();
        my_state.components[self.0 as usize].is_running = true;
    }

    fn stop(self, state: &mut dyn State) {
        let my_state: &mut MyState = state.get_mut();
        my_state.components[self.0 as usize].is_running = false;
    }
}

impl_stop_and_drop!(for MyState {
    fn is_stopped(&self) -> bool {
        self.components.iter().all(|x| !x.is_running)
    }

    fn stop(state: &mut dyn State) {
        for n in 0 .. 32 {
            ComponentId(n).stop(state);
        }
    }
});

let my_state: &mut dyn State = &mut MyState::default();
ComponentId(17).run(my_state);
MyState::stop(my_state); // this line commented ==
                         // panic!("MyState requires \
                         //         explicit stop function call \
                         //         before dropping")