1 #![feature(unboxed_closures)]
2 
3 trait Lt<'a> {
4     type T;
5 }
6 impl<'a> Lt<'a> for () {
7     type T = ();
8 }
9 
main()10 fn main() {
11     let v: <() as Lt<'_>>::T = ();
12     let f: &mut dyn FnMut<(_,), Output = ()> = &mut |_: <() as Lt<'_>>::T| {};
13     //~^ ERROR: the size for values of type `<() as Lt<'_>>::T` cannot be known
14     f(v);
15 }
16