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()10fn 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