// check-pass #![feature(unboxed_closures)] fn is_fn Fn<(&'a (),)>>() {} fn is_fn2 Fn<(&'a &'b (),)>>() {} struct Outlives<'a, 'b>(std::marker::PhantomData<&'a &'b ()>); fn main() { is_fn:: fn(&'a ()) -> &'a ()>(); is_fn:: fn(&'a ()) -> &'a dyn std::fmt::Debug>(); is_fn2:: fn(&'a &'b ()) -> Outlives<'a, 'b>>(); is_fn2:: fn(&'a &'b ()) -> (&'a (), &'a ())>(); }