#![feature(impl_trait_in_fn_trait_return)] use std::fmt::Debug; fn a() -> impl Fn(&u8) -> impl Debug + '_ { //~^ ERROR ambiguous `+` in a type //~| ERROR higher kinded lifetime bounds on nested opaque types are not supported yet |x| x } fn b() -> impl Fn() -> impl Debug + Send { //~^ ERROR ambiguous `+` in a type || () } fn main() {}