fn server() -> impl { //~^ ERROR at least one trait must be specified ().map2(|| "") } trait FilterBase2 { fn map2<F>(self, f: F) -> Map2<F> {} //~^ ERROR mismatched types //~^^ ERROR the size for values of type `Self` cannot be known at compilation time } struct Map2<Segment2> { _func: F, //~^ ERROR cannot find type `F` in this scope } impl<F> FilterBase2 for F {} fn main() {}