attempt1-error.txt

pebble.rs/src/pebble/mod.rs:72:41: 72:49 error: the trait `pebble::WindowWidget` is not implemented for the type `Box<pebble::WindowWidget>` [E0277]
pebble.rs/src/pebble/mod.rs:72         let ret: &'a mut WindowWidget = &mut *br;
                                                                       ^~~~~~~~
pebble.rs/src/pebble/mod.rs:72:41: 72:49 help: run `rustc --explain E0277` to see a detailed explanation
pebble.rs/src/pebble/mod.rs:72:41: 72:49 note: required for the cast to the object type `pebble::WindowWidget + 'a`

attempt1.rs

    fn window_widget_from_raw_ptr<'a>(p: &'a mut *mut types::_Window) -> &'a mut WindowWidget {
        let mut ws: &'a mut WindowStack = unsafe { &mut *(external::window_get_user_data(*p) as *mut _) };
        let br: &'a mut Box<WindowWidget> = ws.windows.get_mut(*p as u32).unwrap();
        let ret: &'a mut WindowWidget = &mut *br;
        ret
    }

attempt2-success.rs

    fn window_widget_from_raw_ptr<'a>(p: &'a mut *mut types::_Window) -> &'a mut WindowWidget {
        let mut ws: &'a mut WindowStack = unsafe { &mut *(external::window_get_user_data(*p) as *mut _) };
        let br: &'a mut Box<WindowWidget> = ws.windows.get_mut(*p as u32).unwrap();
        let ret: &'a mut WindowWidget = &mut **br;
        ret
    }

attempt3-error.txt

pebble.rs/src/pebble/mod.rs:75:9: 75:16 error: the trait `pebble::WindowWidget` is not implemented for the type `&mut Box<pebble::WindowWidget>` [E0277]
pebble.rs/src/pebble/mod.rs:75         &mut br
                                       ^~~~~~~
pebble.rs/src/pebble/mod.rs:75:9: 75:16 help: run `rustc --explain E0277` to see a detailed explanation
pebble.rs/src/pebble/mod.rs:75:9: 75:16 note: required for the cast to the object type `pebble::WindowWidget + 'a`

attempt3.rs

    fn window_widget_from_raw_ptr<'a>(p: &'a mut *mut types::_Window) -> &'a mut WindowWidget {
        let mut ws: &'a mut WindowStack = unsafe { &mut *(external::window_get_user_data(*p) as *mut _) };
        let mut br = ws.windows.get_mut(*p as u32).unwrap();
        &mut br
    }