//~^ ERROR the parameter type `T` may not live long enough
//~| HELP consider adding an explicit lifetime bound
//~| NOTE ...so that the reference type `&'a [T]` does not outlive the data it points at
+//~| HELP run `rustc --explain E0309` to see a detailed explanation
}
impl<'a, T: ListItem<'a>> Collection for List<'a, T> {
fn len(&self) -> usize {