server() -> impl1 fn server() -> impl {
2 //~^ ERROR at least one trait must be specified
3     ().map2(|| "")
4 }
5 
6 trait FilterBase2 {
map2<F>(self, f: F) -> Map2<F>7     fn map2<F>(self, f: F) -> Map2<F> {}
8     //~^ ERROR mismatched types
9     //~^^ ERROR the size for values of type `Self` cannot be known at compilation time
10 }
11 
12 struct Map2<Segment2> {
13     _func: F,
14     //~^ ERROR cannot find type `F` in this scope
15 }
16 
17 impl<F> FilterBase2 for F {}
18 
main()19 fn main() {}
20