Indeed, the way you would be generic over generic closures would be "type HRTB" (e.g. F: for<T: Clone> Fn(&T) -> T), which depends on the trait system overhaul,

Indeed, the way you would be generic over generic closures would be "type HRTB" (e.g. F: for<T: Clone> Fn(&T) -> T), which depends on the trait system overhaul, just like ATC.