fn call_this(f: F) : Fn(&str) + call_that {} //~^ ERROR return types are denoted using `->` //~| ERROR cannot find trait `call_that` in this scope //~| WARN trait objects without an explicit `dyn` are deprecated //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021! fn main() {}