| //@ build-pass | |
| #![feature(trait_upcasting)] | |
| pub trait A {} | |
| pub trait B {} | |
| pub trait C: A + B {} | |
| impl<X: A + B> C for X {} | |
| pub fn test<'a, T>(view: T) -> Option<&'a mut dyn B> | |
| where | |
| T: IntoIterator<Item = &'a mut dyn B>, | |
| { | |
| return Some(view.into_iter().next().unwrap()); | |
| } | |
| fn main() { | |
| let mut a: Vec<Box<dyn C>> = Vec::new(); | |
| test(a.iter_mut().map(|c| c.as_mut() as &mut dyn B)); | |
| } |